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• java.lang.IllegalArgumentException: Method must not be null

  - by abc

  Nested in org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.beans.factory.config.PropertyPlaceholderConfigurer#0': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Method must not be null:java.lang.IllegalArgumentException: Method must not be null i am getting this deployment error while deploying my application. java -version java version "1.6.0_20" Java(TM) SE Runtime Environment (build 1.6.0_20-b02) Java HotSpot(TM) Server VM (build 16.3-b01, mixed mode) while the same build gets deployed successfully in the same server jetty 6.1.3 with following conf. java version "1.6.0_17" spring version used is 2.5.6.SEC01 how to overcome, googling didnt work? 2010-05-13 15:53:20.903::WARN: Failed startup of context org.mortbay.jetty.webapp.WebAppContext@9ad840{/caw,jar:file:/home/jigar/jetty-6.1.3/webapps/caw.war!/} org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.beans.factory.config.PropertyPlaceholderConfigurer#0': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Method must not be null at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:480) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:515) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:362) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:530) at org.mortbay.jetty.servlet.Context.startContext(Context.java:135) at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1218) at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:500) at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:147) at org.mortbay.jetty.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:161) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:147) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.jetty.Server.doStart(Server.java:210) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.xml.XmlConfiguration.main(XmlConfiguration.java:929) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.mortbay.start.Main.invokeMain(Main.java:183) at org.mortbay.start.Main.start(Main.java:497) at org.mortbay.start.Main.main(Main.java:115) Caused by: java.lang.IllegalArgumentException: Method must not be null at org.springframework.util.Assert.notNull(Assert.java:112) at org.springframework.core.BridgeMethodResolver.findBridgedMethod(BridgeMethodResolver.java:63) at org.springframework.beans.GenericTypeAwarePropertyDescriptor.<init>(GenericTypeAwarePropertyDescriptor.java:58) at org.springframework.beans.CachedIntrospectionResults.<init>(CachedIntrospectionResults.java:250) at org.springframework.beans.CachedIntrospectionResults.forClass(CachedIntrospectionResults.java:144) at org.springframework.beans.BeanWrapperImpl.getCachedIntrospectionResults(BeanWrapperImpl.java:252) at org.springframework.beans.BeanWrapperImpl.getPropertyDescriptorInternal(BeanWrapperImpl.java:282) at org.springframework.beans.BeanWrapperImpl.isWritableProperty(BeanWrapperImpl.java:333) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1247) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) ... 35 more 2010-05-13 15:53:20.906::WARN: Nested in org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.beans.factory.config.PropertyPlaceholderConfigurer#0': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Method must not be null: java.lang.IllegalArgumentException: Method must not be null at org.springframework.util.Assert.notNull(Assert.java:112) at org.springframework.core.BridgeMethodResolver.findBridgedMethod(BridgeMethodResolver.java:63) at org.springframework.beans.GenericTypeAwarePropertyDescriptor.<init>(GenericTypeAwarePropertyDescriptor.java:58) at org.springframework.beans.CachedIntrospectionResults.<init>(CachedIntrospectionResults.java:250) at org.springframework.beans.CachedIntrospectionResults.forClass(CachedIntrospectionResults.java:144) at org.springframework.beans.BeanWrapperImpl.getCachedIntrospectionResults(BeanWrapperImpl.java:252) at org.springframework.beans.BeanWrapperImpl.getPropertyDescriptorInternal(BeanWrapperImpl.java:282) at org.springframework.beans.BeanWrapperImpl.isWritableProperty(BeanWrapperImpl.java:333) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1247) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:515) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:362) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:530) at org.mortbay.jetty.servlet.Context.startContext(Context.java:135) at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1218) at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:500) at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:147) at org.mortbay.jetty.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:161) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:147) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.jetty.Server.doStart(Server.java:210) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.xml.XmlConfiguration.main(XmlConfiguration.java:929) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.mortbay.start.Main.invokeMain(Main.java:183) at org.mortbay.start.Main.start(Main.java:497) at org.mortbay.start.Main.main(Main.java:115) 2010-05-13 15:53:20.964::INFO: Started SelectChannelConnector @ 0.0.0.0:8090

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• How to add a specific method to a particular scope in Visual Studion 2005

  - by pragadheesh

  Hi, In my visual studio project (C++), when i copy a method(meth1) of a particular scope say 'scope1' and paste it in the same code area, it is getting pasted in General Scope. i.e I want to add a method into a particular scope but when i try it is getting added in general scope. How can i solve this? For eg: There is an existing method: void add(int a, int b) { .... } This method is in File scope. i.e limited for that file. Now i want to add another method add2 in the same file scope. So I copied the existing add method and pasted it. void add2(int a, int b) { .... } But this method is getting added in the global scope and not in the file scope.

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• Call a macro every time any method is called - Objective C

  - by Jacob Relkin

  Hi, I wrote a debug macro that prints to the console the passed-in string whenever the global kDebug flag == YES. I need to print out the name of a method and it's classname whenever any method is called. That works fine when i painstakingly go through every method and write the name of the class and the method in a string. Is there any special handler that gets called when any method in Objective-C is called, and if so, is there a way i can somehow override it to call my debug macro?? The entire purpose of this is so that I don't have to go through every method in my code and hand-code the method signature in the debug macro call. Thanks

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• No-argument method on window.external is invoked when checking with typeof

  - by janko

  Hi, I am trying to display an HTML page with embedded JavaScript code inside a System.Windows.Forms.WebBrowser control. The JavaScript code is expected to interact with the embedding environment through the window.external object. Before invoking a method on window.external, JavaScript is supposed to check for the existance of the method. If it is not there, the code should invoke a generic fallback method. // basic idea if (typeof(window.external.MyMethod) != 'undefined') { window.external.MyMethod(args); } else { window.external.Generic("MyMethod", args); } However, checking for a no-argument method with typeof seems to invoke the method already. That is, if MyMethod accepts any positive number of arguments, the code above will work perfectly; but, if MyMethod is a no-argument method, then the expression typeof(window.external.MyMethod) will not check for its type but invoke it, too. Is there any work-around to this behavior? Can I somehow escape the expression window.external.MyMethod to prevent the method call from occurring?

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• A Taxonomy of Numerical Methods v1

  - by JoshReuben

  Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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• Is your test method self-validating ?

  - by mehfuzh

  Writing state of art unit tests that can validate your every part of the framework is challenging and interesting at the same time, its like becoming a samurai. One of the key concept in this is to keep our test synced all the time as underlying code changes and thus breaking them to the furthest unit as possible.  This also means, we should avoid  multiple conditions embedded in a single test. Let’s consider the following example of transfer funds. [Fact] public void ShouldAssertTranserFunds() {     var currencyService = Mock.Create<ICurrencyService>();     //// current rate     Mock.Arrange(() => currencyService.GetConversionRate("AUS", "CAD")).Returns(0.88f);       Account to = new Account { Currency = "AUS", Balance = 120 };     Account from = new Account { Currency = "CAD" };       AccountService accService = new AccountService(currencyService);       Assert.Throws<InvalidOperationException>(() => accService.TranferFunds(to, from, 200f));       accService.TranferFunds(to, from, 100f);       Assert.Equal(from.Balance, 88);     Assert.Equal(20, to.Balance); } At first look,  it seems ok but as you look more closely , it is actually doing two tasks in one test. At line# 10 it is trying to validate the exception for invalid fund transfer and finally it is asserting if the currency conversion is successfully made. Here, the name of the test itself is pretty vague. The first rule for writing unit test should always reflect to inner working of the target code, where just by looking at their names it is self explanatory. Having a obscure name for a test method not only increase the chances of cluttering the test code, but it also gives the opportunity to add multiple paths into it and eventually makes things messy as possible. I would rater have two test methods that explicitly describes its intent and are more self-validating. ShouldThrowExceptionForInvalidTransferOperation ShouldAssertTransferForExpectedConversionRate Having, this type of breakdown also helps us pin-point reported bugs easily rather wasting any time on debugging for something more general and can minimize confusion among team members. Finally, we should always make our test F.I.R.S.T ( Fast.Independent.Repeatable.Self-validating.Timely) [ Bob martin – Clean Code]. Only this will be enough to ensure, our test is as simple and clean as possible.   Hope that helps

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• C#/.NET Little Wonders: The Generic Func Delegates

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Back in one of my three original “Little Wonders” Trilogy of posts, I had listed generic delegates as one of the Little Wonders of .NET.  Later, someone posted a comment saying said that they would love more detail on the generic delegates and their uses, since my original entry just scratched the surface of them. Last week, I began our look at some of the handy generic delegates built into .NET with a description of delegates in general, and the Action family of delegates.  For this week, I’ll launch into a look at the Func family of generic delegates and how they can be used to support generic, reusable algorithms and classes. Quick Delegate Recap Delegates are similar to function pointers in C++ in that they allow you to store a reference to a method.  They can store references to either static or instance methods, and can actually be used to chain several methods together in one delegate. Delegates are very type-safe and can be satisfied with any standard method, anonymous method, or a lambda expression.  They can also be null as well (refers to no method), so care should be taken to make sure that the delegate is not null before you invoke it. Delegates are defined using the keyword delegate, where the delegate’s type name is placed where you would typically place the method name: 1: // This delegate matches any method that takes string, returns nothing 2: public delegate void Log(string message); This delegate defines a delegate type named Log that can be used to store references to any method(s) that satisfies its signature (whether instance, static, lambda expression, etc.). Delegate instances then can be assigned zero (null) or more methods using the operator = which replaces the existing delegate chain, or by using the operator += which adds a method to the end of a delegate chain: 1: // creates a delegate instance named currentLogger defaulted to Console.WriteLine (static method) 2: Log currentLogger = Console.Out.WriteLine; 3:  4: // invokes the delegate, which writes to the console out 5: currentLogger("Hi Standard Out!"); 6:  7: // append a delegate to Console.Error.WriteLine to go to std error 8: currentLogger += Console.Error.WriteLine; 9:  10: // invokes the delegate chain and writes message to std out and std err 11: currentLogger("Hi Standard Out and Error!"); While delegates give us a lot of power, it can be cumbersome to re-create fairly standard delegate definitions repeatedly, for this purpose the generic delegates were introduced in various stages in .NET.  These support various method types with particular signatures. Note: a caveat with generic delegates is that while they can support multiple parameters, they do not match methods that contains ref or out parameters. If you want to a delegate to represent methods that takes ref or out parameters, you will need to create a custom delegate. We’ve got the Func… delegates Just like it’s cousin, the Action delegate family, the Func delegate family gives us a lot of power to use generic delegates to make classes and algorithms more generic.  Using them keeps us from having to define a new delegate type when need to make a class or algorithm generic. Remember that the point of the Action delegate family was to be able to perform an “action” on an item, with no return results.  Thus Action delegates can be used to represent most methods that take 0 to 16 arguments but return void.  You can assign a method The Func delegate family was introduced in .NET 3.5 with the advent of LINQ, and gives us the power to define a function that can be called on 0 to 16 arguments and returns a result.  Thus, the main difference between Action and Func, from a delegate perspective, is that Actions return nothing, but Funcs return a result. The Func family of delegates have signatures as follows: Func<TResult> – matches a method that takes no arguments, and returns value of type TResult. Func<T, TResult> – matches a method that takes an argument of type T, and returns value of type TResult. Func<T1, T2, TResult> – matches a method that takes arguments of type T1 and T2, and returns value of type TResult. Func<T1, T2, …, TResult> – and so on up to 16 arguments, and returns value of type TResult. These are handy because they quickly allow you to be able to specify that a method or class you design will perform a function to produce a result as long as the method you specify meets the signature. For example, let’s say you were designing a generic aggregator, and you wanted to allow the user to define how the values will be aggregated into the result (i.e. Sum, Min, Max, etc…).  To do this, we would ask the user of our class to pass in a method that would take the current total, the next value, and produce a new total.  A class like this could look like: 1: public sealed class Aggregator<TValue, TResult> 2: { 3: // holds method that takes previous result, combines with next value, creates new result 4: private Func<TResult, TValue, TResult> _aggregationMethod; 5:  6: // gets or sets the current result of aggregation 7: public TResult Result { get; private set; } 8:  9: // construct the aggregator given the method to use to aggregate values 10: public Aggregator(Func<TResult, TValue, TResult> aggregationMethod = null) 11: { 12: if (aggregationMethod == null) throw new ArgumentNullException("aggregationMethod"); 13:  14: _aggregationMethod = aggregationMethod; 15: } 16:  17: // method to add next value 18: public void Aggregate(TValue nextValue) 19: { 20: // performs the aggregation method function on the current result and next and sets to current result 21: Result = _aggregationMethod(Result, nextValue); 22: } 23: } Of course, LINQ already has an Aggregate extension method, but that works on a sequence of IEnumerable<T>, whereas this is designed to work more with aggregating single results over time (such as keeping track of a max response time for a service). We could then use this generic aggregator to find the sum of a series of values over time, or the max of a series of values over time (among other things): 1: // creates an aggregator that adds the next to the total to sum the values 2: var sumAggregator = new Aggregator<int, int>((total, next) => total + next); 3:  4: // creates an aggregator (using static method) that returns the max of previous result and next 5: var maxAggregator = new Aggregator<int, int>(Math.Max); So, if we were timing the response time of a web method every time it was called, we could pass that response time to both of these aggregators to get an idea of the total time spent in that web method, and the max time spent in any one call to the web method: 1: // total will be 13 and max 13 2: int responseTime = 13; 3: sumAggregator.Aggregate(responseTime); 4: maxAggregator.Aggregate(responseTime); 5:  6: // total will be 20 and max still 13 7: responseTime = 7; 8: sumAggregator.Aggregate(responseTime); 9: maxAggregator.Aggregate(responseTime); 10:  11: // total will be 40 and max now 20 12: responseTime = 20; 13: sumAggregator.Aggregate(responseTime); 14: maxAggregator.Aggregate(responseTime); The Func delegate family is useful for making generic algorithms and classes, and in particular allows the caller of the method or user of the class to specify a function to be performed in order to generate a result. What is the result of a Func delegate chain? If you remember, we said earlier that you can assign multiple methods to a delegate by using the += operator to chain them.  So how does this affect delegates such as Func that return a value, when applied to something like the code below? 1: Func<int, int, int> combo = null; 2:  3: // What if we wanted to aggregate the sum and max together? 4: combo += (total, next) => total + next; 5: combo += Math.Max; 6:  7: // what is the result? 8: var comboAggregator = new Aggregator<int, int>(combo); Well, in .NET if you chain multiple methods in a delegate, they will all get invoked, but the result of the delegate is the result of the last method invoked in the chain.  Thus, this aggregator would always result in the Math.Max() result.  The other chained method (the sum) gets executed first, but it’s result is thrown away: 1: // result is 13 2: int responseTime = 13; 3: comboAggregator.Aggregate(responseTime); 4:  5: // result is still 13 6: responseTime = 7; 7: comboAggregator.Aggregate(responseTime); 8:  9: // result is now 20 10: responseTime = 20; 11: comboAggregator.Aggregate(responseTime); So remember, you can chain multiple Func (or other delegates that return values) together, but if you do so you will only get the last executed result. Func delegates and co-variance/contra-variance in .NET 4.0 Just like the Action delegate, as of .NET 4.0, the Func delegate family is contra-variant on its arguments.  In addition, it is co-variant on its return type.  To support this, in .NET 4.0 the signatures of the Func delegates changed to: Func<out TResult> – matches a method that takes no arguments, and returns value of type TResult (or a more derived type). Func<in T, out TResult> – matches a method that takes an argument of type T (or a less derived type), and returns value of type TResult(or a more derived type). Func<in T1, in T2, out TResult> – matches a method that takes arguments of type T1 and T2 (or less derived types), and returns value of type TResult (or a more derived type). Func<in T1, in T2, …, out TResult> – and so on up to 16 arguments, and returns value of type TResult (or a more derived type). Notice the addition of the in and out keywords before each of the generic type placeholders.  As we saw last week, the in keyword is used to specify that a generic type can be contra-variant -- it can match the given type or a type that is less derived.  However, the out keyword, is used to specify that a generic type can be co-variant -- it can match the given type or a type that is more derived. On contra-variance, if you are saying you need an function that will accept a string, you can just as easily give it an function that accepts an object.  In other words, if you say “give me an function that will process dogs”, I could pass you a method that will process any animal, because all dogs are animals.  On the co-variance side, if you are saying you need a function that returns an object, you can just as easily pass it a function that returns a string because any string returned from the given method can be accepted by a delegate expecting an object result, since string is more derived.  Once again, in other words, if you say “give me a method that creates an animal”, I can pass you a method that will create a dog, because all dogs are animals. It really all makes sense, you can pass a more specific thing to a less specific parameter, and you can return a more specific thing as a less specific result.  In other words, pay attention to the direction the item travels (parameters go in, results come out).  Keeping that in mind, you can always pass more specific things in and return more specific things out. For example, in the code below, we have a method that takes a Func<object> to generate an object, but we can pass it a Func<string> because the return type of object can obviously accept a return value of string as well: 1: // since Func<object> is co-variant, this will access Func<string>, etc... 2: public static string Sequence(int count, Func<object> generator) 3: { 4: var builder = new StringBuilder(); 5:  6: for (int i=0; i<count; i++) 7: { 8: object value = generator(); 9: builder.Append(value); 10: } 11:  12: return builder.ToString(); 13: } Even though the method above takes a Func<object>, we can pass a Func<string> because the TResult type placeholder is co-variant and accepts types that are more derived as well: 1: // delegate that's typed to return string. 2: Func<string> stringGenerator = () => DateTime.Now.ToString(); 3:  4: // This will work in .NET 4.0, but not in previous versions 5: Sequence(100, stringGenerator); Previous versions of .NET implemented some forms of co-variance and contra-variance before, but .NET 4.0 goes one step further and allows you to pass or assign an Func<A, BResult> to a Func<Y, ZResult> as long as A is less derived (or same) as Y, and BResult is more derived (or same) as ZResult. Sidebar: The Func and the Predicate A method that takes one argument and returns a bool is generally thought of as a predicate.  Predicates are used to examine an item and determine whether that item satisfies a particular condition.  Predicates are typically unary, but you may also have binary and other predicates as well. Predicates are often used to filter results, such as in the LINQ Where() extension method: 1: var numbers = new[] { 1, 2, 4, 13, 8, 10, 27 }; 2:  3: // call Where() using a predicate which determines if the number is even 4: var evens = numbers.Where(num => num % 2 == 0); As of .NET 3.5, predicates are typically represented as Func<T, bool> where T is the type of the item to examine.  Previous to .NET 3.5, there was a Predicate<T> type that tended to be used (which we’ll discuss next week) and is still supported, but most developers recommend using Func<T, bool> now, as it prevents confusion with overloads that accept unary predicates and binary predicates, etc.: 1: // this seems more confusing as an overload set, because of Predicate vs Func 2: public static SomeMethod(Predicate<int> unaryPredicate) { } 3: public static SomeMethod(Func<int, int, bool> binaryPredicate) { } 4:  5: // this seems more consistent as an overload set, since just uses Func 6: public static SomeMethod(Func<int, bool> unaryPredicate) { } 7: public static SomeMethod(Func<int, int, bool> binaryPredicate) { } Also, even though Predicate<T> and Func<T, bool> match the same signatures, they are separate types!  Thus you cannot assign a Predicate<T> instance to a Func<T, bool> instance and vice versa: 1: // the same method, lambda expression, etc can be assigned to both 2: Predicate<int> isEven = i => (i % 2) == 0; 3: Func<int, bool> alsoIsEven = i => (i % 2) == 0; 4:  5: // but the delegate instances cannot be directly assigned, strongly typed! 6: // ERROR: cannot convert type... 7: isEven = alsoIsEven; 8:  9: // however, you can assign by wrapping in a new instance: 10: isEven = new Predicate<int>(alsoIsEven); 11: alsoIsEven = new Func<int, bool>(isEven); So, the general advice that seems to come from most developers is that Predicate<T> is still supported, but we should use Func<T, bool> for consistency in .NET 3.5 and above. Sidebar: Func as a Generator for Unit Testing One area of difficulty in unit testing can be unit testing code that is based on time of day.  We’d still want to unit test our code to make sure the logic is accurate, but we don’t want the results of our unit tests to be dependent on the time they are run. One way (of many) around this is to create an internal generator that will produce the “current” time of day.  This would default to returning result from DateTime.Now (or some other method), but we could inject specific times for our unit testing.  Generators are typically methods that return (generate) a value for use in a class/method. For example, say we are creating a CacheItem<T> class that represents an item in the cache, and we want to make sure the item shows as expired if the age is more than 30 seconds.  Such a class could look like: 1: // responsible for maintaining an item of type T in the cache 2: public sealed class CacheItem<T> 3: { 4: // helper method that returns the current time 5: private static Func<DateTime> _timeGenerator = () => DateTime.Now; 6:  7: // allows internal access to the time generator 8: internal static Func<DateTime> TimeGenerator 9: { 10: get { return _timeGenerator; } 11: set { _timeGenerator = value; } 12: } 13:  14: // time the item was cached 15: public DateTime CachedTime { get; private set; } 16:  17: // the item cached 18: public T Value { get; private set; } 19:  20: // item is expired if older than 30 seconds 21: public bool IsExpired 22: { 23: get { return _timeGenerator() - CachedTime > TimeSpan.FromSeconds(30.0); } 24: } 25:  26: // creates the new cached item, setting cached time to "current" time 27: public CacheItem(T value) 28: { 29: Value = value; 30: CachedTime = _timeGenerator(); 31: } 32: } Then, we can use this construct to unit test our CacheItem<T> without any time dependencies: 1: var baseTime = DateTime.Now; 2:  3: // start with current time stored above (so doesn't drift) 4: CacheItem<int>.TimeGenerator = () => baseTime; 5:  6: var target = new CacheItem<int>(13); 7:  8: // now add 15 seconds, should still be non-expired 9: CacheItem<int>.TimeGenerator = () => baseTime.AddSeconds(15); 10:  11: Assert.IsFalse(target.IsExpired); 12:  13: // now add 31 seconds, should now be expired 14: CacheItem<int>.TimeGenerator = () => baseTime.AddSeconds(31); 15:  16: Assert.IsTrue(target.IsExpired); Now we can unit test for 1 second before, 1 second after, 1 millisecond before, 1 day after, etc.  Func delegates can be a handy tool for this type of value generation to support more testable code.  Summary Generic delegates give us a lot of power to make truly generic algorithms and classes.  The Func family of delegates is a great way to be able to specify functions to calculate a result based on 0-16 arguments.  Stay tuned in the weeks that follow for other generic delegates in the .NET Framework!   Tweet Technorati Tags: .NET, C#, CSharp, Little Wonders, Generics, Func, Delegates

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• RemoveAll Dictionary Extension Method

  - by João Angelo

  Removing from a dictionary all the elements where the keys satisfy a set of conditions is something I needed to do more than once so I implemented it as an extension method to the IDictionary<TKey, TValue> interface. Here’s the code: public static class DictionaryExtensions { /// <summary> /// Removes all the elements where the key match the conditions defined by the specified predicate. /// </summary> /// <typeparam name="TKey"> /// The type of the dictionary key. /// </typeparam> /// <typeparam name="TValue"> /// The type of the dictionary value. /// </typeparam> /// <param name="dictionary"> /// A dictionary from which to remove the matched keys. /// </param> /// <param name="match"> /// The <see cref="Predicate{T}"/> delegate that defines the conditions of the keys to remove. /// </param> /// <exception cref="ArgumentNullException"> /// dictionary is null /// <br />-or-<br /> /// match is null. /// </exception> /// <returns> /// The number of elements removed from the <see cref="IDictionary{TKey, TValue}"/>. /// </returns> public static int RemoveAll<TKey, TValue>( this IDictionary<TKey, TValue> dictionary, Predicate<TKey> match) { if (dictionary == null) throw new ArgumentNullException("dictionary"); if (match == null) throw new ArgumentNullException("match"); var keysToRemove = dictionary.Keys.Where(k => match(k)).ToList(); if (keysToRemove.Count == 0) return 0; foreach (var key in keysToRemove) { dictionary.Remove(key); } return keysToRemove.Count; } }

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• Helper method to Replace/Remove characters that do not match the Regular Expression

  - by Michael Freidgeim

  I have a few fields, that use regEx for validation. In case if provided field has unaccepted characters, I don't want to reject the whole field, as most of validators do, but just remove invalid characters. I am expecting to keep only Character Classes for allowed characters and created a helper method to strip unaccepted characters. The allowed pattern should be in Regex format, expect them wrapped in square brackets. function will insert a tilde after opening squere bracket , according to http://stackoverflow.com/questions/4460290/replace-chars-if-not-match.  [^ ] at the start of a character class negates it - it matches characters not in the class.I anticipate that it could work not for all RegEx describing valid characters sets,but it works for relatively simple sets, that we are using.         /// <summary>               /// Replaces  not expected characters.               /// </summary>               /// <param name="text"> The text.</param>               /// <param name="allowedPattern"> The allowed pattern in Regex format, expect them wrapped in brackets</param>               /// <param name="replacement"> The replacement.</param>               /// <returns></returns>               /// //        http://stackoverflow.com/questions/4460290/replace-chars-if-not-match.               //http://stackoverflow.com/questions/6154426/replace-remove-characters-that-do-not-match-the-regular-expression-net               //[^ ] at the start of a character class negates it - it matches characters not in the class.               //Replace/Remove characters that do not match the Regular Expression               static public string ReplaceNotExpectedCharacters( this string text, string allowedPattern,string replacement )              {                     allowedPattern = allowedPattern.StripBrackets( "[", "]" );                      //[^ ] at the start of a character class negates it - it matches characters not in the class.                      var result = Regex .Replace(text, @"[^" + allowedPattern + "]", replacement);                      return result;              }static public string RemoveNonAlphanumericCharacters( this string text)              {                      var result = text.ReplaceNotExpectedCharacters(NonAlphaNumericCharacters, "" );                      return result;              }        public const string NonAlphaNumericCharacters = "[a-zA-Z0-9]";There are a couple of functions from my StringHelper class  http://geekswithblogs.net/mnf/archive/2006/07/13/84942.aspx , that are used here.    //                           /// <summary>               /// 'StripBrackets checks that starts from sStart and ends with sEnd (case sensitive).               ///           'If yes, than removes sStart and sEnd.               ///           'Otherwise returns full string unchanges               ///           'See also MidBetween               /// </summary>               /// <param name="str"></param>               /// <param name="sStart"></param>               /// <param name="sEnd"></param>               /// <returns></returns>               public static string StripBrackets( this string str, string sStart, string sEnd)              {                      if (CheckBrackets(str, sStart, sEnd))                     {                           str = str.Substring(sStart.Length, (str.Length - sStart.Length) - sEnd.Length);                     }                      return str;              }               public static bool CheckBrackets( string str, string sStart, string sEnd)              {                      bool flag1 = (str != null ) && (str.StartsWith(sStart) && str.EndsWith(sEnd));                      return flag1;              }               public static string WrapBrackets( string str, string sStartBracket, string sEndBracket)              {                      StringBuilder builder1 = new StringBuilder(sStartBracket);                     builder1.Append(str);                     builder1.Append(sEndBracket);                      return builder1.ToString();              }v

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• Software Architecture Analysis Method (SAAM)

  Software Architecture Analysis Method (SAAM) is a methodology used to determine how specific application quality attributes were achieved and how possible changes in the future will affect quality attributes based on hypothetical cases studies. Common quality attributes that can be utilized by this methodology include modifiability, robustness, portability, and extensibility. Quality Attribute: Application Modifiability The Modifiability quality attribute refers to how easy it changing the system in the future will be. This to me is a very open-ended attribute because a business could decide to transform a Point of Sale (POS) system in to a Lead Tracking system overnight. (Yes, this did actually happen to me) In order for SAAM to be properly applied for checking this attribute specific hypothetical case studies need to be created and review for the modifiability attribute due to the fact that various scenarios would return various results based on the amount of changes. In the case of the POS change out a payment gateway or adding an additional payment would have scored very high in comparison to changing the system over to a lead management system. I personally would evaluate this quality attribute based on the S.O.I.L.D Principles of software design. I have found from my experience the use of S.O.I.L.D in software design allows for the adoption of changes within a system. Quality Attribute: Application Robustness The Robustness quality attribute refers to how an application handles the unexpected. The unexpected can be defined but is not limited to anything not anticipated in the originating design of the system. For example: Bad Data, Limited to no network connectivity, invalid permissions, or any unexpected application exceptions. I would personally evaluate this quality attribute based on how the system handled the exceptions. Robustness Considerations Did the system stop or did it handle the unexpected error? Did the system log the unexpected error for future debugging? What message did the user receive about the error? Quality Attribute: Application Portability The Portability quality attribute refers to the ease of porting an application to run in a new operating system or device. For example, It is much easier to alter an ASP.net website to be accessible by a PC, Mac, IPhone, Android Phone, Mini PC, or Table in comparison to desktop application written in VB.net because a lot more work would be involved to get the desktop app to the point where it would be viable to port the application over to the various environments and devices. I would personally evaluate this quality attribute based on each new environment for which the hypothetical case study identifies. I would pay particular attention to the following items. Portability Considerations Hardware Dependencies Operating System Dependencies Data Source Dependencies Network Dependencies and Availabilities  Quality Attribute: Application Extensibility The Extensibility quality attribute refers to the ease of adding new features to an existing application without impacting existing functionality. I would personally evaluate this quality attribute based on each new environment for the following Extensibility  Considerations Hard coded Variables versus Configurable variables Application Documentation (External Documents and Codebase Documentation.) The use of Solid Design Principles

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• Best depth sorting method for a Top Down 2D game using a 3D physics engine

  - by Alic44

  I've spent many days googling this and still have issues with my game engine I'd like to ask about, which I haven't seen addressed before. I think the problem is that my game is an unusual combination of a completely 2D graphical approach using XNA's SpriteBatch, and a completely 3D engine (the amazing BEPU physics engine) with rotation mostly disabled. In essence, my question is similar to this one (the part about "faux 3D"), but the difference is that in my game, the player as well as every other creature is represented by 3D objects, and they can all jump, pick up other objects, and throw them around. What this means is that sorting by one value, such as a Z position (how far north/south a character is on the screen) won't work, because as soon as a smaller creature jumps on top of a larger creature, or a box, and walks backwards, the moment its z value is less than that other creature, it will appear to be behind the object it is actually standing on. I actually originally solved this problem by splitting every object in the game into physics boxes which MUST have a Y height equal to their Z depth. I then based the depth sorting value on the object's y position (how high it is off the ground) PLUS its z position (how far north or south it is on the screen). The problem with this approach is that it requires all moving objects in the game to be split graphically into chunks which match up with a physical box which has its y dimension equal to its z dimension. Which is stupid. So, I got inspired last night to rewrite with a fresh approach. My new method is a little more complex, but I think a little more sane: every object which needs to be sorted by depth in the game exposes the interface IDepthDrawable and is added to a list owned by the DepthDrawer object. IDepthDrawable contains: public interface IDepthDrawable { Rectangle Bounds { get; } //possibly change this to a class if struct copying of the xna Rectangle type becomes an issue DepthDrawShape DepthShape { get; } void Draw(SpriteBatch spriteBatch); } The Bounds Rectangle of each IDepthDrawable object represents the 2D Axis-Aligned Bounding Box it will take up when drawn to the screen. Anything that doesn't intersect the screen will be culled at this stage and the remaining on-screen IDepthDrawables will be Bounds tested for intersections with each other. This is where I get a little less sure of what I'm doing. Each group of collisions will be added to a list or other collection, and each list will sort itself based on its DepthShape property, which will have access to the object-to-be-drawn's physics information. For starting out, lets assume everything in the game is an axis aligned 3D Box shape. Boxes are pretty easy to sort. Something like: if (depthShape1.Back > depthShape2.Front) //if depthShape1 is in front of depthShape2. //depthShape1 goes on top. else if (depthShape1.Bottom > depthShape2.Top) //if depthShape1 is above depthShape2. //depthShape1 goes on top. //if neither of these are true, depthShape2 must be in front or above. So, by sorting draw order by several different factors from the physics engine, I believe I can get a really correct draw order. My question is, is this a good way of going about this, or is there some tried and true, tested way which is completely different and has somehow completely eluded me on the internets? And, if this does seem like a good way to remake my draw order sorting, what's the right sorting algorithm for reordering the Bounds Rectangle collision lists, and how do you deal with a Bounds Rectangle colliding with two different object which don't collide with eachother. I know these are solved problems, but I've only been programming for a year so any specific input here will be greatly appreciated. Thanks for reading this far, ye who made it -- sorry it was so long!

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• Magento My Account Layout XML Problem

  - by Remy

  Hi there, I'm having issues getting the customer.xml layout file to work properly for the customer's "my account" pages. The navigation links and the previously ordered items that are usually on the left hand side of the page won't show up on the page, but if I change the reference name to "content" in the xml file, it shows up (except it's obviously then on the right hand side). I've checked the template it's referencing (2columns-left.phtml), and the getChildHtml('left') is there in the correct position. The block that's causing the problem: <customer_account> <!-- Mage_Customer --> <reference name="root"> <action method="setTemplate"><template>page/2columns-left.phtml</template></action> </reference> <reference name="left"> <action method="unsetChild"><name>catalog.navigation.all</name></action> <action method="unsetChild"><name>callout.sendcard</name></action> <action method="unsetChild"><name>callout.specialorder</name></action> <block type="customer/account_navigation" name="customer_account_navigation" before="-" template="customer/account/navigation.phtml"> <action method="addLink" translate="label" module="customer"><name>account</name><path>customer/account/</path><label>Account Dashboard</label></action> <action method="addLink" translate="label" module="customer"><name>account_edit</name><path>customer/account/edit/</path><label>Account Information</label></action> <action method="addLink" translate="label" module="customer"><name>address_book</name><path>customer/address/</path><label>Address Book</label></action> </block> <block type="sales/reorder_sidebar" name="sale.reorder.sidebar" as="reorder" template="sales/reorder/sidebar.phtml"/> <remove name="tags_popular"/> </reference> </customer_account> This was basically copied straight over from another one of our sites where this works 100%. I've tried everything I can think of (changing the name of the reference in both the template and the layout xml, for example) to no avail. The templates that the layout is referencing are obviously working because they do show up when put into the "content" area. This installation of magento is version 1.3.1.1. I appreciate any advice you have to give me... *Update: I tried changing the reference to "global_messages", and it doesn't show there either. It only seems to work in the "content" section.* Update 2: These are the results of using the "showLayout=page" query string on the page when used with Alan Storm's very handy debugging module (which you'll find in his answer below). <?xml version="1.0"?> <layout><block type="page/html" name="root" output="toHtml" template="page/3columns.phtml"> <block type="page/html_head" name="head" as="head"> <action method="addJs"> <script>prototype/prototype.js</script> </action> <action method="addJs"> <script>prototype/validation.js</script> </action> <action method="addJs"> <script>paypoint/validation.js</script> </action> <action method="addJs"> <script>scriptaculous/builder.js</script> </action> <action method="addJs"> <script>scriptaculous/effects.js</script> </action> <action method="addJs"> <script>scriptaculous/dragdrop.js</script> </action> <action method="addJs"> <script>scriptaculous/controls.js</script> </action> <action method="addJs"> <script>scriptaculous/slider.js</script> </action> <action method="addJs"> <script>varien/js.js</script> </action> <action method="addJs"> <script>varien/form.js</script> </action> <action method="addJs"> <script>varien/menu.js</script> </action> <action method="addJs"> <script>mage/translate.js</script> </action> <action method="addJs"> <script>mage/cookies.js</script> </action> <action method="addCss"> <stylesheet>css/reset.css</stylesheet> </action> <action method="addCss"> <stylesheet>css/boxes.css</stylesheet> </action> <action method="addCss"> <stylesheet>css/clears.css</stylesheet> </action> <action method="addCss"> <stylesheet>css/menu.css</stylesheet> </action> <action method="addCss"> <stylesheet>css/calendar-blue.css</stylesheet> </action> <action method="addCss"> <stylesheet>css/styles.css</stylesheet> </action> <action method="addItem"> <type>skin_css</type> <name>css/iestyles.css</name> <params/> <if>IE</if> </action> <action method="addItem"> <type>skin_css</type> <name>css/ie7.css</name> <params/> <if>IE 7</if> </action> <action method="addItem"> <type>skin_css</type> <name>css/ie7minus.css</name> <params/> <if>lt IE 7</if> </action> <action method="addItem"> <type>js</type> <name>lib/ds-sleight.js</name> <params/> <if>lt IE 7</if> </action> <action method="addItem"> <type>js</type> <name>varien/iehover-fix.js</name> <params/> <if>lt IE 7</if> </action> <action method="addCss"> <stylesheet>css/print.css</stylesheet> <params>media="print"</params> </action> </block> <block type="page/html_header" name="header" as="header"> <block type="page/template_links" name="top.links" as="topLinks"/> <block type="page/switch" name="store_language" as="store_language" template="page/switch/languages.phtml"/> <block type="core/template" name="top.nav" template="page/html/top.nav.phtml"/> </block> <block type="core/messages" name="global_messages" as="global_messages"/> <block type="core/messages" name="messages" as="messages"/> <block type="core/text_list" name="content" as="content"/> <block type="core/text_list" name="right" as="right"/> <block type="page/html_footer" name="footer" as="footer" template="page/html/footer.phtml"/> <block type="core/text_list" name="before_body_end" as="before_body_end"/> </block> <block type="core/profiler" output="toHtml"/> <reference name="top.links"> <action method="addLink" translate="label title" module="customer"> <label>My Account</label> <url helper="customer/getAccountUrl"/> <title>My Account</title> <prepare/> <urlParams/> <position>10</position> </action> </reference> <reference name="root"> <action method="setTemplate"> <template>page/2columns-left.phtml</template> </action> </reference> <reference name="top.menu"> <block type="catalog/navigation" name="catalog.topnav" template="catalog/navigation/top.phtml"/> </reference> <reference name="footer_links"> <action method="addLink" translate="label title" module="catalog" ifconfig="catalog/seo/site_map"> <label>Site Map</label> <url helper="catalog/map/getCategoryUrl"/> <title>Site Map</title> </action> </reference> <reference name="footer_links"> <action method="addLink" translate="label title" module="catalogsearch" ifconfig="catalog/seo/search_terms"> <label>Search Terms</label> <url helper="catalogsearch/getSearchTermUrl"/> <title>Search Terms</title> </action> <action method="addLink" translate="label title" module="catalogsearch"> <label>Advanced Search</label> <url helper="catalogsearch/getAdvancedSearchUrl"/> <title>Advanced Search</title> </action> </reference> <reference name="top.links"> <block type="checkout/links" name="checkout_cart_link"> <action method="addCartLink"/> <action method="addCheckoutLink"/> </block> </reference> <reference name="footer"> <block type="cms/block" name="cms_footer_links" before="footer_links"> <action method="setBlockId"> <block_id>footer_links</block_id> </action> </block> </reference> <reference name="left"> <block type="tag/popular" name="tags_popular" template="tag/popular.phtm" ignore="1"> <action method="setTemplate"> <template>tag/popular.phtml</template> </action> </block> </reference> <reference name="left"> </reference> <reference name="before_body_end"> <block type="googleanalytics/ga" name="google_analytics" as="google_analytics"/> </reference> <reference name="footer_links"> <action method="addLink" translate="label title" module="contacts" ifconfig="contacts/contacts/enabled"> <label>Contact Us</label> <url>contact-us</url> <title>Contact Us</title> <prepare>true</prepare> </action> </reference> <reference name="footer_links"> <action method="addLink" translate="label title" module="rss" ifconfig="rss/config/active"> <label>RSS</label> <url>rss</url> <title>RSS testing</title> <prepare>true</prepare> <urlParams/> <position/> <li/> <a>class="link-feed"</a> </action> </reference> <reference name="wishlist_sidebar"> <action method="addPriceBlockType"> <type>bundle</type> <block>bundle/catalog_product_price</block> <template>bundle/catalog/product/price.phtml</template> </action> </reference> <reference name="cart_sidebar"> <action method="addItemRender"> <type>bundle</type> <block>bundle/checkout_cart_item_renderer</block> <template>checkout/cart/sidebar/default.phtml</template> </action> </reference> <reference name="root"> <action method="setTemplate"> <template>page/2columns-left.phtml</template> </action> </reference> <reference name="left"> <action method="unsetChild"> <name>catalog.navigation.all</name> </action> <action method="unsetChild"> <name>callout.sendcard</name> </action> <action method="unsetChild"> <name>callout.specialorder</name> </action> <block type="customer/account_navigation" name="customer_account_navigation" before="-" template="customer/account/navigation.phtml"> <action method="addLink" translate="label" module="customer"> <name>account</name> <path>customer/account/</path> <label>Account Dashboard</label> </action> <action method="addLink" translate="label" module="customer"> <name>account_edit</name> <path>customer/account/edit/</path> <label>Account Information</label> </action> <action method="addLink" translate="label" module="customer"> <name>address_book</name> <path>customer/address/</path> <label>Address Book</label> </action> </block> <block type="sales/reorder_sidebar" name="sale.reorder.sidebar" as="reorder" template="sales/reorder/sidebar.phtml"/> <remove name="tags_popular"/> </reference> <reference name="customer_account_navigation"> <action method="addLink" translate="label" module="sales"> <name>orders</name> <path>sales/order/history/</path> <label>My Orders</label> </action> </reference> <reference name="customer_account_navigation"> <action method="addLink" translate="label" module="tag"> <name>tags</name> <path>tag/customer/</path> <label>My Tags</label> </action> </reference> <reference name="customer_account_navigation"> <action method="addLink" translate="label" module="newsletter"> <name>newsletter</name> <path>newsletter/manage/</path> <label>Newsletter Subscriptions</label> </action> </reference> <reference name="cart_sidebar"> <action method="addItemRender"> <type>bundle</type> <block>bundle/checkout_cart_item_renderer</block> <template>checkout/cart/sidebar/default.phtml</template> </action> </reference> <update handle="customer_account"/> <reference name="content"> <block type="customer/account_dashboard" name="customer_account_dashboard" template="customer/account/dashboard.phtml"> <block type="customer/account_dashboard_hello" name="customer_account_dashboard_hello" as="hello" template="customer/account/dashboard/hello.phtml"/> <block type="core/template" name="customer_account_dashboard_top" as="top"/> <block type="customer/account_dashboard_info" name="customer_account_dashboard_info" as="info" template="customer/account/dashboard/info.phtml"/> <block type="customer/account_dashboard_newsletter" name="customer_account_dashboard_newsletter" as="newsletter" template="customer/account/dashboard/newsletter.phtml"/> <block type="customer/account_dashboard_address" name="customer_account_dashboard_address" as="address" template="customer/account/dashboard/address.phtml"/> <block type="core/template" name="customer_account_dashboard_info1" as="info1"/> <block type="core/template" name="customer_account_dashboard_info2" as="info2"/> </block> </reference> <reference name="right"> <action method="unsetChild"> <name>catalog_compare_sidebar</name> </action> </reference> <reference name="customer_account_dashboard"> <action method="unsetChild"> <name>top</name> </action> <block type="sales/order_recent" name="customer_account_dashboard_top" as="top" template="sales/order/recent.phtml"/> </reference> <reference name="right"> <action method="unsetChild"> <name>right.poll</name> </action> </reference> <reference name="customer_account_dashboard"> <action method="unsetChild"> <name>customer_account_dashboard_info2</name> </action> <block type="tag/customer_recent" name="customer_account_dashboard_info2" as="info2" template="tag/customer/recent.phtml"/> </reference> <reference name="right"> <action method="unsetChild"> <name>right.newsletter</name> </action> </reference> <reference name="top.links"> <action method="addLink" translate="label title" module="customer"> <label>Log Out</label> <url helper="customer/getLogoutUrl"/> <title>Log Out</title> <prepare/> <urlParams/> <position>100</position> </action> </reference></layout>

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• Objective C: Initalizing static variable with static method call

  - by adranale

  The Compiler claims an error saying: "initializer element is not constant", when I try to initialize a static variable inside a method with a call to a static method (with + in its definition). Anyway I can tell him that this method always returns the same value. I know this is not the same as static method, but there seems to be no constant methods in Objective-C (other than macros which won't work here because I am calling UI_USER_INTERFACE_IDIOM() from inside the method).

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• How to check how many threads are waiting for a synchronized method to become unlocked

  - by MontyBongo

  Is there any way to check how many threads are waiting for a synchronized method to become unlocked? I would like to know when the thread calls a synchronized method: 1) How many threads are already waiting to call the method? 2) Once the method is called how long it needed to wait for the method to become unlocked?

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• Oracle HRMS API – Create Employee Payment Method

  - by PRajkumar

  API --  hr_personal_pay_method_api.create_personal_pay_method   Example -- DECLARE   ln_method_id  PAY_PERSONAL_PAYMENT_METHODS_F.PERSONAL_PAYMENT_METHOD_ID%TYPE; ln_ext_acc_id        PAY_EXTERNAL_ACCOUNTS.EXTERNAL_ACCOUNT_ID%TYPE; ln_obj_ver_num    PAY_PERSONAL_PAYMENT_METHODS_F.OBJECT_VERSION_NUMBER%TYPE; ld_eff_start_date   DATE;   ld_eff_end_date    DATE; ln_comment_id     NUMBER; BEGIN      -- Create Employee Payment Method      -- --------------------------------------------------       hr_personal_pay_method_api.create_personal_pay_method       (   -- Input data elements           -- ------------------------------           p_effective_date                                     => TO_DATE('21-JUN-2011'),           p_assignment_id                                   => 33561,           p_org_payment_method_id               => 2,           p_priority                                                 => 50,           p_percentage                                           => 100,           p_territory_code                                     => 'US',           p_segment1                                              => 'PRAJKUMAR',           p_segment2                                              => 'S',           p_segment3                                              => '100200300',           p_segment4                                              => '567',           p_segment5                                              => 'HDFC',           p_segment6                                              => 'INDIA',           -- Output data elements           -- --------------------------------           p_personal_payment_method_id   => ln_method_id,           p_external_account_id                       => ln_ext_acc_id,           p_object_version_number                  => ln_obj_ver_num,           p_effective_start_date                          => ld_eff_start_date,           p_effective_end_date                           => ld_eff_end_date,          p_comment_id                                        => ln_comment_id      );    COMMIT; EXCEPTION           WHEN OTHERS THEN                           ROLLBACK;                            dbms_output.put_line(SQLERRM); END; / SHOW ERR;    

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• Struct Method for Loops Problem

  - by Annalyne

  I have tried numerous times how to make a do-while loop using the float constructor for my code but it seems it does not work properly as I wanted. For summary, I am making a TBRPG in C++ and I encountered few problems. But before that, let me post my code. #include <iostream> #include <string> #include <ctime> #include <cstdlib> using namespace std; int char_level = 1; //the starting level of the character. string town; //town string town_name; //the name of the town the character is in. string charname; //holds the character's name upon the start of the game int gems = 0; //holds the value of the games the character has. const int MAX_ITEMS = 15; //max items the character can carry string inventory [MAX_ITEMS]; //the inventory of the character in game int itemnum = 0; //number of items that the character has. bool GameOver = false; //boolean intended for the game over scr. string monsterTroop [] = {"Slime", "Zombie", "Imp", "Sahaguin, Hounds, Vampire"}; //monster name float monsterTroopHealth [] = {5.0f, 10.0f, 15.0f, 20.0f, 25.0f}; // the health of the monsters int monLifeBox; //life carrier of the game's enemy troops int enemNumber; //enemy number //inventory[itemnum++] = "Sword"; class RPG_Game_Enemy { public: void enemyAppear () { srand(time(0)); enemNumber = 1+(rand()%3); if (enemNumber == 1) cout << monsterTroop[1]; //monster troop 1 else if (enemNumber == 2) cout << monsterTroop[2]; //monster troop 2 else if (enemNumber == 3) cout << monsterTroop[3]; //monster troop 3 else if (enemNumber == 4) cout << monsterTroop[4]; //monster troop 4 } void enemDefeat () { cout << "The foe has been defeated. You are victorious." << endl; } void enemyDies() { //if the enemy dies: //collapse declaration cout << "The foe vanished and you are victorious!" << endl; } }; class RPG_Scene_Battle { public: RPG_Scene_Battle(float ini_health) : health (ini_health){}; float getHealth() { return health; } void setHealth(float rpg_val){ health = rpg_val;}; private: float health; }; //---------------------------------------------------------------// // Conduct Damage for the Scene Battle's Damage //---------------------------------------------------------------// float conductDamage(RPG_Scene_Battle rpg_tr, float damage) { rpg_tr.setHealth(rpg_tr.getHealth() - damage); return rpg_tr.getHealth(); }; // ------------------------------------------------------------- // void RPG_Scene_DisplayItem () { cout << "Items: \n"; for (int i=0; i < itemnum; ++i) cout << inventory[i] <<endl; }; In this code I have so far, the problem I have is the battle scene. For example, the player battles a Ghost with 10 HP, when I use a do while loop to subtract the HP of the character and the enemy, it only deducts once in the do while. Some people said I should use a struct, but I have no idea how to make it. Is there a way someone can display a code how to implement it on my game? Edit: I made the do-while by far like this: do RPG_Scene_Battle (player, 20.0f); RPG_Scene_Battle (enemy, 10.0f); cout << "Battle starts!" <<endl; cout << "You used a blade skill and deducted 2 hit points to the enemy!" conductDamage (enemy, 2.0f); while (enemy!=0) also, I made something like this: #include <iostream> using namespace std; int gems = 0; class Entity { public: Entity(float startingHealth) : health(startingHealth){}; // initialize health float getHealth(){return health;} void setHealth(float value){ health = value;}; private: float health; }; float subtractHealthFrom(Entity& ent, float damage) { ent.setHealth(ent.getHealth() - damage); return ent.getHealth(); }; int main () { Entity character(10.0f); Entity enemy(10.0f); cout << "Hero Life: "; cout << subtractHealthFrom(character, 2.0f) <<endl; cout << "Monster Life: "; cout << subtractHealthFrom(enemy, 2.0f) <<endl; cout << "Hero Life: "; cout << subtractHealthFrom(character, 2.0f) <<endl; cout << "Monster Life: "; cout << subtractHealthFrom(enemy, 2.0f) <<endl; }; Struct method, they say, should solve this problem. How can I continously deduct hp from the enemy? Whenever I deduct something, it would return to its original value -_-

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• Invoking callhierarchy for a method

  - by Steven

  hi, I have an object of type IMethod which represents a method .I want to get the Call Hierarchy of this method . Which methods should i call to get the call hierarchy of a method? Is there any method by which i can do it? I know that i can get it by ctrl+alt+H but i want the code or method for invoking it. Thanks

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• Method-Object pairs in Java

  - by John Manak

  I'd like to create a list of method-object pairs. Each method is a function returning a boolean. Then: foreach(pair) { if method evaluates to true { do something with the object } } One way of modelling this that I can think of is to have a class Constraint with a method isValid() and for each constraint produce an anonymous class (overriding the isValid() method). I feel like there could be a nicer way. Can you think of any?

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• Removing SCIM input method as default from gnome terminal

  - by Mark

  Hello - I am recently back into the Linux world after about a 10 year absence. While I can find my way around most things, terminals and desktop managers are different than I remember. One of the biggest problems that I am encountering today is that when running a gnome terminal (this is Suse 10.0 enterprise), I'm getting behavior in the window that I don't want. Specifically, when I type, my typing is underlined as if something is trying to spell check my window. Further, it seems as if when running vi or less, my keystrokes are only processed by these apps when I hit 'return'. I.e. if I'm running less and want to go back a page, I'll hit b, but nothing happens until I hit 'return'. I seem to have tracked this down to the 'input method". Right clicking in the Gnome terminal allows me to set my input method to one of a dozen values. It seems that currently, it's set to "SCIM Input Method". If I then select 'default' or 'X Input Method', apps (i.e. things like less, vi, and even the bash shell) behave as I would expect. Can someone tell me a) what is this SCIM input method b) how can I make it so that it is not the default? I've poked around various configuration files in my home directory as well as in /etc, but I can't see to find how this is set. I guess as a final question, can I just get rid of SCIM? Or is that tied into the window manager somehow? I do appreciate any clarifications that I can get. Thanks.

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• Enumerable Interleave Extension Method

  - by João Angelo

  A recent stackoverflow question, which I didn’t bookmark and now I’m unable to find, inspired me to implement an extension method for Enumerable that allows to insert a constant element between each pair of elements in a sequence. Kind of what String.Join does for strings, but maintaining an enumerable as the return value. Having done the single element part I got a bit carried away and ended up expanding it adding overloads to support interleaving elements of another sequence and support for a predicate to control when interleaving takes place. I have to confess that I did this for fun and now I can’t think of any real usage scenario, nonetheless, it may prove useful for someone. First a simple example: var target = new string[] { "(", ")", "(", ")" }; var result = target.Interleave(".", (f, s) => f == "("); // Prints: (.)(.) Console.WriteLine(String.Join(string.Empty, result)); And now the untested but documented implementation: using System; using System.Collections; using System.Collections.Generic; using System.Linq; public static class EnumerableExtensions { /// <summary> /// Iterates infinitely over a constant element. /// </summary> /// <typeparam name="T"> /// The type of element in the sequence. /// </typeparam> private class InfiniteSequence<T> : IEnumerable<T>, IEnumerator<T> { public InfiniteSequence(T element) { this.Element = element; } public T Element { get; private set; } public IEnumerator<T> GetEnumerator() { return this; } IEnumerator IEnumerable.GetEnumerator() { return this; } T IEnumerator<T>.Current { get { return this.Element; } } void IDisposable.Dispose() { } object IEnumerator.Current { get { return this.Element; } } bool IEnumerator.MoveNext() { return true; } void IEnumerator.Reset() { } } /// <summary> /// Interleaves the specified <paramref name="element"/> between each pair of elements in the <paramref name="target"/> sequence. /// </summary> /// <typeparam name="T"> /// The type of elements in the sequence. /// </typeparam> /// <param name="target"> /// The target sequence to be interleaved. /// </param> /// <param name="element"> /// The element used to perform the interleave operation. /// </param> /// <exception cref="ArgumentNullException"> /// <paramref name="target"/> or <paramref name="element"/> is a null reference. /// </exception> /// <returns> /// The <paramref name="target"/> sequence interleaved with the specified <paramref name="element"/>. /// </returns> public static IEnumerable<T> Interleave<T>( this IEnumerable<T> target, T element) { if (target == null) throw new ArgumentNullException("target"); if (element == null) throw new ArgumentNullException("element"); return InterleaveInternal(target, new InfiniteSequence<T>(element), (f, s) => true); } /// <summary> /// Interleaves the specified <paramref name="element"/> between each pair of elements in the <paramref name="target"/> sequence. /// </summary> /// <remarks> /// The interleave operation is interrupted as soon as the <paramref name="target"/> sequence is exhausted; If the number of <paramref name="elements"/> to be interleaved are not enough to completely interleave the <paramref name="target"/> sequence then the remainder of the sequence is returned without being interleaved. /// </remarks> /// <typeparam name="T"> /// The type of elements in the sequence. /// </typeparam> /// <param name="target"> /// The target sequence to be interleaved. /// </param> /// <param name="elements"> /// The elements used to perform the interleave operation. /// </param> /// <exception cref="ArgumentNullException"> /// <paramref name="target"/> or <paramref name="element"/> is a null reference. /// </exception> /// <returns> /// The <paramref name="target"/> sequence interleaved with the specified <paramref name="elements"/>. /// </returns> public static IEnumerable<T> Interleave<T>( this IEnumerable<T> target, IEnumerable<T> elements) { if (target == null) throw new ArgumentNullException("target"); if (elements == null) throw new ArgumentNullException("elements"); return InterleaveInternal(target, elements, (f, s) => true); } /// <summary> /// Interleaves the specified <paramref name="element"/> between each pair of elements in the <paramref name="target"/> sequence that satisfy <paramref name="predicate"/>. /// </summary> /// <typeparam name="T"> /// The type of elements in the sequence. /// </typeparam> /// <param name="target"> /// The target sequence to be interleaved. /// </param> /// <param name="element"> /// The element used to perform the interleave operation. /// </param> /// <param name="predicate"> /// A predicate used to assert if interleaving should occur between two target elements. /// </param> /// <exception cref="ArgumentNullException"> /// <paramref name="target"/> or <paramref name="element"/> or <paramref name="predicate"/> is a null reference. /// </exception> /// <returns> /// The <paramref name="target"/> sequence interleaved with the specified <paramref name="element"/>. /// </returns> public static IEnumerable<T> Interleave<T>( this IEnumerable<T> target, T element, Func<T, T, bool> predicate) { if (target == null) throw new ArgumentNullException("target"); if (element == null) throw new ArgumentNullException("element"); if (predicate == null) throw new ArgumentNullException("predicate"); return InterleaveInternal(target, new InfiniteSequence<T>(element), predicate); } /// <summary> /// Interleaves the specified <paramref name="element"/> between each pair of elements in the <paramref name="target"/> sequence that satisfy <paramref name="predicate"/>. /// </summary> /// <remarks> /// The interleave operation is interrupted as soon as the <paramref name="target"/> sequence is exhausted; If the number of <paramref name="elements"/> to be interleaved are not enough to completely interleave the <paramref name="target"/> sequence then the remainder of the sequence is returned without being interleaved. /// </remarks> /// <typeparam name="T"> /// The type of elements in the sequence. /// </typeparam> /// <param name="target"> /// The target sequence to be interleaved. /// </param> /// <param name="elements"> /// The elements used to perform the interleave operation. /// </param> /// <param name="predicate"> /// A predicate used to assert if interleaving should occur between two target elements. /// </param> /// <exception cref="ArgumentNullException"> /// <paramref name="target"/> or <paramref name="element"/> or <paramref name="predicate"/> is a null reference. /// </exception> /// <returns> /// The <paramref name="target"/> sequence interleaved with the specified <paramref name="elements"/>. /// </returns> public static IEnumerable<T> Interleave<T>( this IEnumerable<T> target, IEnumerable<T> elements, Func<T, T, bool> predicate) { if (target == null) throw new ArgumentNullException("target"); if (elements == null) throw new ArgumentNullException("elements"); if (predicate == null) throw new ArgumentNullException("predicate"); return InterleaveInternal(target, elements, predicate); } private static IEnumerable<T> InterleaveInternal<T>( this IEnumerable<T> target, IEnumerable<T> elements, Func<T, T, bool> predicate) { var targetEnumerator = target.GetEnumerator(); if (targetEnumerator.MoveNext()) { var elementsEnumerator = elements.GetEnumerator(); while (true) { T first = targetEnumerator.Current; yield return first; if (!targetEnumerator.MoveNext()) yield break; T second = targetEnumerator.Current; bool interleave = true && predicate(first, second) && elementsEnumerator.MoveNext(); if (interleave) yield return elementsEnumerator.Current; } } } }

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• Writing a method to 'transform' an immutable object: how should I approach this?

  - by Prog

  (While this question has to do with a concrete coding dilemma, it's mostly about what's the best way to design a function.) I'm writing a method that should take two Color objects, and gradually transform the first Color into the second one, creating an animation. The method will be in a utility class. My problem is that Color is an immutable object. That means that I can't do color.setRGB or color.setBlue inside a loop in the method. What I can do, is instantiate a new Color and return it from the method. But then I won't be able to gradually change the color. So I thought of three possible solutions: 1- The client code includes the method call inside a loop. For example: int duration = 1500; // duration of the animation in milliseconds int steps = 20; // how many 'cycles' the animation will take for(int i=0; i<steps; i++) color = transformColor(color, targetColor, duration, steps); And the method would look like this: Color transformColor(Color original, Color target, int duration, int steps){ int redDiff = target.getRed() - original.getRed(); int redAddition = redDiff / steps; int newRed = original.getRed() + redAddition; // same for green and blue .. Thread.sleep(duration / STEPS); // exception handling omitted return new Color(newRed, newGreen, newBlue); } The disadvantage of this approach is that the client code has to "do part of the method's job" and include a for loop. The method doesn't do it's work entirely on it's own, which I don't like. 2- Make a mutable Color subclass with methods such as setRed, and pass objects of this class into transformColor. Then it could look something like this: void transformColor(MutableColor original, Color target, int duration){ final int STEPS = 20; int redDiff = target.getRed() - original.getRed(); int redAddition = redDiff / steps; int newRed = original.getRed() + redAddition; // same for green and blue .. for(int i=0; i<STEPS; i++){ original.setRed(original.getRed() + redAddition); // same for green and blue .. Thread.sleep(duration / STEPS); // exception handling omitted } } Then the calling code would usually look something like this: // The method will usually transform colors of JComponents JComponent someComponent = ... ; // setting the Color in JComponent to be a MutableColor Color mutableColor = new MutableColor(someComponent.getForeground()); someComponent.setForeground(mutableColor); // later, transforming the Color in the JComponent transformColor((MutableColor)someComponent.getForeground(), new Color(200,100,150), 2000); The disadvantage is - the need to create a new class MutableColor, and also the need to do casting. 3- Pass into the method the actual mutable object that holds the color. Then the method could do object.setColor or similar every iteration of the loop. Two disadvantages: A- Not so elegant. Passing in the object that holds the color just to transform the color feels unnatural. B- While most of the time this method will be used to transform colors inside JComponent objects, other kinds of objects may have colors too. So the method would need to be overloaded to receive other types, or receive Objects and have instanceof checks inside.. Not optimal. Right now I think I like solution #2 the most, than solution #1 and solution #3 the least. However I'd like to hear your opinions and suggestions regarding this.

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• Factory Method Pattern clarification

  - by nettguy

  My understanding of Factory Method Pattern is (Correct me if i am wrong) Factory Method Pattern "Factory Method allow the client to delegates the product creation (Instance Creation) to the subclass". There are two situation in which we can go for creating Factory Method pattern. (i) When the client is restricted to the product (Instance) creation. (ii) There are multiple products available.But a decision to be made which product instance need to be returned. If you want to create Abstract Method pattern You need to have abstract product Concrete Product Factory Method to return the appropriate product. Example : public enum ORMChoice { L2SQL, EFM, LS, Sonic } //Abstract Product public interface IProduct { void ProductTaken(); } //Concrete Product public class LinqtoSql : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken:LinqtoSql"); } } //concrete product public class Subsonic : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken:Subsonic"); } } //concrete product public class EntityFramework : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken:EntityFramework"); } } //concrete product public class LightSpeed : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken :LightSpeed"); } } public class Creator { //Factory Method public IProduct ReturnORTool(ORMChoice choice) { switch (choice) { case ORMChoice.EFM:return new EntityFramework(); break; case ORMChoice.L2SQL:return new LinqtoSql(); break; case ORMChoice.LS:return new LightSpeed(); break; case ORMChoice.Sonic:return new Subsonic(); break; default: return null; } } } **Client** Button_Click() { Creator c = new Creator(); IProduct p = c.ReturnORTool(ORMChoice.L2SQL); p.ProductTaken(); } Is my understanding of Factory Method is correct?

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• algorithm || method to write prog

  - by fatai

  I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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• Most awkward/misleading method in Java Base API ?

  - by JG

  I was recently trying to convert a string literal into a boolean, when the method "boolean Boolean.getBoolean(String name)" popped out of the auto-complete window. There was also another method ("boolean Boolean.parseBoolean(String s)") appearing right after, which lead me to search to find out what were the differences between these two, as they both seemed to do the same. It turns out that what Boolean.getBoolean(String name) really does is to check if there exists a System property (!) of the given name and if its value is true. I think this is very misleading, as I'm definitely not expecting that a method of Boolean is actually making a call to System.getProperty, and just by looking at the method signature, it sure looks (at least to me) like it should be used to parse a String as a boolean. Sure, the javadoc states it clearly, but I still think the method has a misleading name and is not in the right place. Other primitive type wrappers, such as Integer also have a similar method. Also, it doesn't seem to be a very useful method to belong in the base API, as I think it's not very common to have something like -Darg=true. Maybe it's a good question for a Java position interview: "What is the output of Boolean.getBoolean("true")?". I believe a more appropriate place for those methods would be in the System class, e.g., getPropertyAsBoolean; but again, I still think it's unnecessary to have these methods in the base API. It'd make sense to have these in something like the Properties class, where it's very common to do this kind of type conversions. What do you think of all this ? Also, if there's another "awkward" method that you're aware of, please post it. N.B. I know I can use Boolean.valueOf or Boolean.parseBoolean to convert a string literal into a boolean, but I'm just looking to discuss the API design.

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• What are Bridge and Synthetic methods in Java?

  - by kunjaan

  Returns : true if and only if this method is a bridge method as defined by the Java Language Specification. Since: 1.5 Returns: true if and only if this method is a synthetic method as defined by the Java Language Specification. Since: 1.5 I saw these in my Reflection doc. I saw couple of docs but I couldn't fully understand the usage of them. Could Somebody expalin these methods for a layperson?

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