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  • Extreme Optimization –Mathematical Constants and Basic Functions

    - by JoshReuben
    Machine constants The MachineConstants class - contains constants for floating-point arithmetic because the CLS System.Single and Double floating-point types do not follow the standard conventions and are useless. machine constants for the Double type: machine precision: Epsilon , SqrtEpsilon CubeRootEpsilon largest possible value: MaxDouble , SqrtMaxDouble, LogMaxDouble smallest Double-precision floating point number that is greater than zero: MinDouble , SqrtMinDouble , LogMinDouble A similar set of constants is available for the Single Datatype  Mathematical Constants The Constants class contains static fields for many mathematical constants and common expressions involving small integers – if you are doing thousands of iterations, you wouldn't want to calculate OneOverSqrtTwoPi , Sqrt17 or Log17 !!! Fundamental constants E - The base for the natural logarithm, e (2.718...). EulersConstant - (0.577...). GoldenRatio - (1.618...). Pi - the ratio between the circumference and the diameter of a circle (3.1415...). Expressions involving fundamental constants: TwoPi, PiOverTwo, PiOverFour, LogTwoPi, PiSquared, SqrPi, SqrtTwoPi, OneOverSqrtPi, OneOverSqrtTwoPi Square roots of small integers: Sqrt2, Sqrt3, Sqrt5, Sqrt7, Sqrt17 Logarithms of small integers: Log2, Log3, Log10, Log17, InvLog10  Elementary Functions The IterativeAlgorithm<T> class in the Extreme.Mathematics namespace defines many elementary functions that are missing from System.Math. Hyperbolic Trig Functions: Cosh, Coth, Csch, Sinh, Sech, Tanh Inverse Hyperbolic Trig Functions: Acosh, Acoth, Acsch, Asinh, Asech, Atanh Exponential, Logarithmic and Miscellaneous Functions: ExpMinus1 - The exponential function minus one, ex-1. Hypot - The hypotenuse of a right-angled triangle with specified sides. LambertW - Lambert's W function, the (real) solution W of x=WeW. Log1PlusX - The natural logarithm of 1+x. Pow - A number raised to an integer power.

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  • Enhance your Queries with Stored Functions

    HeidiSQL 4's Stored Routine Editor offers a user-friendly alternative to using a command-line interface to create and manage your stored procedures and functions. Today, we'll be learning how to take advantage of some useful native MySQL functions as well as use the editor to create our own custom functions.

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  • T-SQL User-Defined Functions: the good, the bad, and the ugly (part 2)

    - by Hugo Kornelis
    In a previous blog post , I demonstrated just how much you can hurt your performance by encapsulating expressions and computations in a user-defined function (UDF). I focused on scalar functions that didn’t include any data access. In this post, I will complete the discussion on scalar UDFs by covering the effect of data access in a scalar UDF. Note that, like the previous post, this all applies to T-SQL user-defined functions only. SQL Server also supports CLR user-defined functions (written in...(read more)

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  • T-SQL User-Defined Functions: the good, the bad, and the ugly (part 3)

    - by Hugo Kornelis
    I showed why T-SQL scalar user-defined functions are bad for performance in two previous posts. In this post, I will show that CLR scalar user-defined functions are bad as well (though not always quite as bad as T-SQL scalar user-defined functions). I will admit that I had not really planned to cover CLR in this series. But shortly after publishing the first part , I received an email from Adam Machanic , which basically said that I should make clear that the information in that post does not apply...(read more)

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  • T-SQL User-Defined Functions: the good, the bad, and the ugly (part 2)

    - by Hugo Kornelis
    In a previous blog post , I demonstrated just how much you can hurt your performance by encapsulating expressions and computations in a user-defined function (UDF). I focused on scalar functions that didn’t include any data access. In this post, I will complete the discussion on scalar UDFs by covering the effect of data access in a scalar UDF. Note that, like the previous post, this all applies to T-SQL user-defined functions only. SQL Server also supports CLR user-defined functions (written in...(read more)

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  • Initiate a PHP class where class name is a variable

    - by ed209
    I need some help with an error I have not encountered before and can't seem to find anywhere. In a PHP mvc framework (just from a tutorial) I have the following: // Initiate the class $className = 'Controller_' . ucfirst($controller); if (class_exists($className)) { $controller = new $className($this->registry); } $className is showing the correct class name (case is also correct). But when I run it I get this in the apache error log (no php error) [Wed Mar 31 10:34:12 2010] [notice] child pid 987 exit signal Segmentation fault (11) Process id is different on every call. I am running PHP 5.3.0 on os x 10.6. This site seems to work on 5.2.11 on another Mac. Not really sure where to go next to debug it. I guess it could be an apache setting as much as a php bug or a problem with the code... any suggestions on where to look next?

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  • T-SQL User-Defined Functions: the good, the bad, and the ugly (part 3)

    - by Hugo Kornelis
    I showed why T-SQL scalar user-defined functions are bad for performance in two previous posts. In this post, I will show that CLR scalar user-defined functions are bad as well (though not always quite as bad as T-SQL scalar user-defined functions). I will admit that I had not really planned to cover CLR in this series. But shortly after publishing the first part , I received an email from Adam Machanic , which basically said that I should make clear that the information in that post does not apply...(read more)

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  • SQL Server Functions: The Basics

    SQL Server's functions are a valuable addition to T-SQL when used wisely. Jeremiah Peshcka provides a complete and comprehensive guide to scalar functions and table-valued functions, and shows how and where they are best used. The Future of SQL Server Monitoring "Being web-based, SQL Monitor enables you to check on your servers from almost any location" Jonathan Allen.Try SQL Monitor now.

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  • Why does Zend discourage "floating functions"?

    - by kojiro
    Zend's Coding Standard Naming Convention says Functions in the global scope (a.k.a "floating functions") are permitted but discouraged in most cases. Consider wrapping these functions in a static class. The common wisdom in Python says practically the opposite: Finally, use staticmethod sparingly! There are very few situations where static-methods are necessary in Python, and I've seen them used many times where a separate "top-level" function would have been clearer. (Not only does the above StackOverflow answer warn against overuse of static methods, but more than one Python linter will warn the same.) Is this something that can be generalized across programming languages, and if so, why does Python differ so from PHP? If it's not something that can be generalized, what is the basis for one approach or the other, and is there a way to immediately recognize in a language whether you should prefer bare functions or static methods?

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  • How are larger games organized?

    - by Matthew G.
    I'm using Java, but the language I'm using here is probably irrelevant. I'd like to create an economy based on an ancient civilization. I'm not sure how to design it. If I were working on a smaller game, like a copy of "Space Invaders", I'd have no problem structuring it like this. Game -Main Control Class --Graphics Class --Player Class --Enemy class I'd pass the graphics class to both the player and enemy class so they could call graphics functions. I don't understand how I'd do this for larger projects. Do I create a country class that contains a bunch of towns? Do the towns contain a lot building class, most contain classes of people? Do I make a path finding class that the player can access to get around? How exactly do I structure this and pass all these references around? Thanks.

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  • Making WatiN Wait for JQuery document.Ready() Functions to Complete

    - by Steve Wilkes
    WatiN's DomContainer.WaitForComplete() method pauses test execution until the DOM has finished loading, but if your page has functions registered with JQuery's ready() function, you'll probably want to wait for those to finish executing before testing it. Here's a WatiN extension method which pauses test execution until that happens. JQuery (as far as I can see) doesn't provide an event or other way of being notified of when it's finished running your ready() functions, so you have to get around it another way. Luckily, because ready() executes the functions it's given in the order they're registered, you can simply register another one to add a 'marker' div to the page, and tell WatiN to wait for that div to exist. Here's the code; I added the extension method to Browser rather than DomContainer (Browser derives from DomContainer) because it's the sort of thing you only execute once for each of the pages your test loads, so Browser seemed like a good place to put it. public static void WaitForJQueryDocumentReadyFunctionsToComplete(this Browser browser) { // Don't try this is JQuery isn't defined on the page: if (bool.Parse(browser.Eval("typeof $ == 'function'"))) { const string jqueryCompleteId = "jquery-document-ready-functions-complete"; // Register a ready() function which adds a marker div to the body: browser.Eval( @"$(document).ready(function() { " + "$('body').append('<div id=""" + jqueryCompleteId + @""" />'); " + "});"); // Wait for the marker div to exist or make the test fail: browser.Div(Find.ById(jqueryCompleteId)) .WaitUntilExistsOrFail(10, "JQuery document ready functions did not complete."); } } The code uses the Eval() method to send JavaScript to the browser to be executed; first to check that JQuery actually exists on the page, then to add the new ready() method. WaitUntilExistsOrFail() is another WatiN extension method I've written (I've ended up writing really quite a lot of them) which waits for the element on which it is invoked to exist, and uses Assert.Fail() to fail the test with the given message if it doesn't exist within the specified number of seconds. Here it is: public static void WaitUntilExistsOrFail(this Element element, int timeoutInSeconds, string failureMessage) { try { element.WaitUntilExists(timeoutInSeconds); } catch (WatinTimeoutException) { Assert.Fail(failureMessage); } }

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  • Single complex or multiple simple autoload functions [on hold]

    - by Tyson of the Northwest
    Using the spl_autoload_register(), should I use a single autoload function that contains all the logic to determine where the include files are or should I break each include grouping into it's own function with it's own logic to include the files for the called function? As the places where include files may reside expands so too will the logic of a single function. If I break it into multiple functions I can add functions as new groupings are added, but the functions will be copy/pastes of each other with minor alterations. Currently I have a tool with a single registered autoload function that picks apart the class name and tries to predict where it is and then includes it. Due to naming conventions for the project this has been pretty simple. if has namespace if in template namespace look in Root\Templates else look in Root\Modules\Namespace else look in Root\System if file exists include But we are starting to include Interfaces and Traits into our codebase and it hurts me to include the type of a thing in it's name. So we are looking at instead of a single autoload function that digs through the class name and looks for the file and has increasingly complex logic to it, we are looking at having multiple autoload functions registered. But each one follows the same pattern and any time I see that I get paranoid about code copying. function systemAutoloadFunc logic to create probable filename if filename exists in system include it and return true else return false function moduleAutoloadFunc logic to create probable filename if filename exists in modules include it and return true else return false Every autoload function will follow that pattern and the last of each function if filename exists, include return true else return false is going to be identical code. This makes me paranoid about having to update it later across the board if the file_exists include pattern we are using ever changes. Or is it just that, paranoia and the multiple functions with some identical code is the best option?

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  • Macro vs. Static functions in Header

    - by wirrbel
    for a lot of quick tasks where one could employ a function f(x,y), in plain C, macros are used. I would like to ask specifically about these cases, that are solvable by a function call (i.e. macros used for inlining functions, not for code expansion of arbitrary code). Typically C functions are not inlined since they might be linked to from other C files. However, static C functions are only visible from within the C file they are defined in. Therefore they can be inlined by compilers. I have heard that a lot of macros should be replaced by turning them into static functions, because this produces safer code. Are there cases where this is a not good idea? Again: Not asking about Code-Production macros with ## alike constructs that cannot at all be expressed as a function.

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  • Window Functions in SQL Server

    When SQL Server introduced Window Functions in SQL Server 2005, it was done in a rather tentative way, with only a handful of functions being introduced. This was frustrating, as they remove the last excuse for cursor-based operations by providing aggregations over a partition of the result set, and imposing an ordered sequence over a partition. Now, with SQL Server 2012, we are soon to enjoy a full range of Window Functions. They are going to make for some much simpler SQL queries.

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  • How to access functions in extended classes efficiently?

    - by nischayn22
    In PHP I have classes as below class Animal { //some vars public function printname(){ echo $this->name; } } class AnimalMySql extends Animal { static public function getTableFields(){ return array(); } } class AnimalPostgreSql extends Animal { static public function getTableFields(){ return array(); } } Now I have an object $lion = new Animal(); and I want to do if($store == mysql) //getTableFields from class AnimalMySql else //getTableFields form class AnimalPostgreSql I am new to OOP and not sure what is the best way to call the method from the specific class P.S. Please leave a note with the answer to explain the efficiency of the approach

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  • Stairway to MDX - Level 10: “Relative” Member Functions: .CurrentMember, .PrevMember, and .NextMember

    SSAS Maestro, SQL Server MVP and Business Intelligence Architect Bill Pearson introduces three “major players” within the MDX “relative” functions. These basic, but highly employed, functions include the .CurrentMember, .PrevMember and .NextMember functions. Check SQL Server performance at a glanceWe consulted 1000 SQL Server professionals to make SQL Monitor’s UI as clear as possible. Start monitoring with a free trial.

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  • Refactoring a leaf class to a base class, and keeping it also a interface implementation

    - by elcuco
    I am trying to refactor a working code. The code basically derives an interface class into a working implementation, and I want to use this implementation outside the original project as a standalone class. However, I do not want to create a fork, and I want the original project to be able to take out their implementation, and use mine. The problem is that the hierarchy structure is very different and I am not sure if this would work. I also cannot use the original base class in my project, since in reality it's quite entangled in the project (too many classes, includes) and I need to take care of only a subdomain of the problems the original project is. I wrote this code to test an idea how to implement this, and while it's working, I am not sure I like it: #include <iostream> // Original code is: // IBase -> Derived1 // I need to refactor Derive2 to be both indipendet class // and programmers should also be able to use the interface class // Derived2 -> MyClass + IBase // MyClass class IBase { public: virtual void printMsg() = 0; }; /////////////////////////////////////////////////// class Derived1 : public IBase { public: virtual void printMsg(){ std::cout << "Hello from Derived 1" << std::endl; } }; ////////////////////////////////////////////////// class MyClass { public: virtual void printMsg(){ std::cout << "Hello from MyClass" << std::endl; } }; class Derived2: public IBase, public MyClass{ virtual void printMsg(){ MyClass::printMsg(); } }; class Derived3: public MyClass, public IBase{ virtual void printMsg(){ MyClass::printMsg(); } }; int main() { IBase *o1 = new Derived1(); IBase *o2 = new Derived2(); IBase *o3 = new Derived3(); MyClass *o4 = new MyClass(); o1->printMsg(); o2->printMsg(); o3->printMsg(); o4->printMsg(); return 0; } The output is working as expected (tested using gcc and clang, 2 different C++ implementations so I think I am safe here): [elcuco@pinky ~/src/googlecode/qtedit4/tools/qtsourceview/qate/tests] ./test1 Hello from Derived 1 Hello from MyClass Hello from MyClass Hello from MyClass [elcuco@pinky ~/src/googlecode/qtedit4/tools/qtsourceview/qate/tests] ./test1.clang Hello from Derived 1 Hello from MyClass Hello from MyClass Hello from MyClass The question is My original code was: class Derived3: public MyClass, public IBase{ virtual void IBase::printMsg(){ MyClass::printMsg(); } }; Which is what I want to express, but this does not compile. I must admit I do not fully understand why this code work, as I expect that the new method Derived3::printMsg() will be an implementation of MyClass::printMsg() and not IBase::printMsg() (even tough this is what I do want). How does the compiler chooses which method to re-implement, when two "sister classes" have the same virtual function name? If anyone has a better way of implementing this, I would like to know as well :)

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  • How does a template class inherit another template class?

    - by hkBattousai
    I have a "SquareMatrix" template class which inherits "Matrix" template class, like below: SquareMatrix.h: #ifndef SQUAREMATRIX_H #define SQUAREMATRIX_H #include "Matrix.h" template <class T> class SquareMatrix : public Matrix<T> { public: T GetDeterminant(); }; template <class T> // line 49 T SquareMatrix<T>::GetDeterminant() { T t = 0; // Error: Identifier "T" is undefined // line 52 return t; // Error: Expected a declaration // line 53 } // Error: Expected a declaration // line 54 #endif I commented out all other lines, the files contents are exactly as above. I receive these error messages: LINE 49: IntelliSense: expected a declaration LINE 52: IntelliSense: expected a declaration LINE 53: IntelliSense: expected a declaration LINE 54: error C2039: 'GetDeterminant' : is not a member of 'SquareMatrix' LINE 54: IntelliSense: expected a declaration So, what is the correct way of inheriting a template class? And what is wrong with this code? The "Matrix" class: template <class T> class Matrix { public: Matrix(uint64_t unNumRows = 0, uint64_t unNumCols = 0); void GetDimensions(uint64_t & unNumRows, uint64_t & unNumCols) const; std::pair<uint64_t, uint64_t> GetDimensions() const; void SetDimensions(uint64_t unNumRows, uint64_t unNumCols); void SetDimensions(std::pair<uint64_t, uint64_t> Dimensions); uint64_t GetRowSize(); uint64_t GetColSize(); void SetElement(T dbElement, uint64_t unRow, uint64_t unCol); T & GetElement(uint64_t unRow, uint64_t unCol); //Matrix operator=(const Matrix & rhs); // Compiler generate this automatically Matrix operator+(const Matrix & rhs) const; Matrix operator-(const Matrix & rhs) const; Matrix operator*(const Matrix & rhs) const; Matrix & operator+=(const Matrix & rhs); Matrix & operator-=(const Matrix & rhs); Matrix & operator*=(const Matrix & rhs); T& operator()(uint64_t unRow, uint64_t unCol); const T& operator()(uint64_t unRow, uint64_t unCol) const; static Matrix Transpose (const Matrix & matrix); static Matrix Multiply (const Matrix & LeftMatrix, const Matrix & RightMatrix); static Matrix Add (const Matrix & LeftMatrix, const Matrix & RightMatrix); static Matrix Subtract (const Matrix & LeftMatrix, const Matrix & RightMatrix); static Matrix Negate (const Matrix & matrix); // TO DO: static bool IsNull(const Matrix & matrix); static bool IsSquare(const Matrix & matrix); static bool IsFullRowRank(const Matrix & matrix); static bool IsFullColRank(const Matrix & matrix); // TO DO: static uint64_t GetRowRank(const Matrix & matrix); static uint64_t GetColRank(const Matrix & matrix); protected: std::vector<T> TheMatrix; uint64_t m_unRowSize; uint64_t m_unColSize; bool DoesElementExist(uint64_t unRow, uint64_t unCol); };

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  • EF4 Code First - Many to many relationship issue

    - by Yngve B. Nilsen
    Hi! I'm having some trouble with my EF Code First model when saving a relation to a many to many relationship. My Models: public class Event { public int Id { get; set; } public string Name { get; set; } public virtual ICollection<Tag> Tags { get; set; } } public class Tag { public int Id { get; set; } public string Name { get; set; } public virtual ICollection<Event> Events { get; set; } } In my controller, I map one or many TagViewModels into type of Tag, and send it down to my servicelayer for persistence. At this time by inspecting the entities the Tag has both Id and Name (The Id is a hidden field, and the name is a textbox in my view) The problem occurs when I now try to add the Tag to the Event. Let's take the following scenario: The Event is already in my database, and let's say it already has the related tags C#, ASP.NET If I now send the following list of tags to the servicelayer: ID Name 1 C# 2 ASP.NET 3 EF4 and add them by first fetching the Event from the DB, so that I have an actual Event from my DbContext, then I simply do myEvent.Tags.Add to add the tags.. Problem is that after SaveChanges() my DB now contains this set of tags: ID Name 1 C# 2 ASP.NET 3 EF4 4 C# 5 ASP.NET This, even though my Tags that I save has it's ID set when I save it (although I didn't fetch it from the DB)

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  • Single Table Per Class Hierarchy with an abstract superclass using Hibernate Annotations

    - by Andy Hull
    I have a simple class hierarchy, similar to the following: @Entity @Table(name="animal") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="animal_type", discriminatorType=DiscriminatorType.STRING) public abstract class Animal { } @Entity @DiscriminatorValue("cat") public class Cat extends Animal { } @Entity @DiscriminatorValue("dog") public class Dog extends Animal { } When I query "from Animal" I get this exception: "org.hibernate.InstantiationException: Cannot instantiate abstract class or interface: Animal" If I make Animal concrete, and add a dummy discriminator... such as @DiscriminatorValue("animal")... my query returns my cats and dogs as instances of Animals. I remember this being trivial with HBM based mappings but I think I'm missing something when using annotations. Can anyone help? Thanks!

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  • Collect all extension methods to generic class in another generic class

    - by Hun1Ahpu
    I'd like to create a lot of extension methods for some generic class, e.g. for public class SimpleLinkedList<T> where T:IComparable And I've started creating methods like this: public static class LinkedListExtensions { public static T[] ToArray<T>(this SimpleLinkedList<T> simpleLinkedList) where T:IComparable { //// code } } But when I tried to make LinkedListExtensions class generic like this: public static class LinkedListExtensions<T> where T:IComparable { public static T[] ToArray(this SimpleLinkedList<T> simpleLinkedList) { ////code } } I get "Extension methods can only be declared in non-generic, non-nested static class". And I'm trying to guess where this restriction came from and have no ideas.

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  • PHP and Classes: access to parent's public property within the parent class

    - by takpar
    Hi, here is what my code looks like i have two forms: class Form_1 extends Form_Abstract { public $iId = 1; } class Form_2 extends Form_1 { public $iId = 2; } i expect the code behave like this: $oForm = new Form_2; echo $oForm->getId(); // it returns '2' echo $oForm->getParentId(); // i expect it returns '1' here is my Form_Abstract class: class Form_Abstract { public $iId = 0; public function getId() { return $this->iId; } /** this method will be called from a child instance */ public function getParentId() { return parent::$iId; } } but it throws a Fatal Error: Fatal error: Cannot access parent:: when current class scope has no parent please help me with the method getParentId()

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  • Return pointer to nested inner class from generic outer class

    - by helixed
    I'm new to C++, so bear with me. I have a generic class called A. A has a nested class called B. A contains a method called getB(), which is supposed to return a new instance of B. However, I can't get my code to compile. Here's what it looks like:#include A.h template <class E> class A { public: class B { public: int data; }; B * getB(); }; A.cpp #include "A.h" template <class E> A<E>::B * A::getB() { return new B(); } When I try to compile this, I get the following error: error: expected constructor, destructor, or type conversion before '*' token Does anybody know what I'm doing wrong? Thanks, helixed

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