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• Oracle Magazine: Getting started with SQL Analytics

  - by KLaker

  I am currently working on a series of podcasts covering the broad categories of our SQL analytical functions and features and while I was doing some research I came across of series of four articles in the Oracle Magazine. This series of article is written by Melanie Caffrey who is a senior development manager at Oracle. She is a coauthor of Expert PL/SQL Practices for Oracle Developers and DBAs (Apress, 2011) and Expert Oracle Practices: Oracle Database Administration from the Oak Table (Apress, 2010). The four articles are under the banner "Technology: SQL 101" and parts 9, 10, 11 and 12 cover SQL analytics. Here are the links to the four articles: Jan 2013 Having Sums, Averages, and Other Grouped Data March 2013 A Window into the World of Analytic Functions May 2013 Leading Ranks and Lagging Percentages: Analytic Functions, Continued July 2013 Pivotal Access to Your Data: Analytic Functions, Concluded The articles cover topics such as GROUP BY, SUM, AVG, HAVING, window functions, RANK, FIRST, LAST, LAG, LEAD etc.   The great news is that  you can try out the examples in this series. All you need is access to an Oracle Database instance. All the schemas, data sets and SQL statements that you will need can be downloaded from a link included in the January article.    I hope you find this series of articles useful.

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• MySQL Multi-Aggregated Rows in Crosstab Queries

  MySQL's crosstabs contain aggregate functions on two or more fields, presented in a tabular format. In a multi-aggregate crosstab query, two different functions can be applied to the same field or the same function can be applied to multiple fields on the same (row or column) axis. Rob Gravelle shows you how to apply two different functions to the same field in order to create grouping levels in the row axis.

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• MySQL Multi-Aggregated Rows in Crosstab Queries

  MySQL's crosstabs contain aggregate functions on two or more fields, presented in a tabular format. In a multi-aggregate crosstab query, two different functions can be applied to the same field or the same function can be applied to multiple fields on the same (row or column) axis. Rob Gravelle shows you how to apply two different functions to the same field in order to create grouping levels in the row axis.

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• What is the ideal length of a method?

  - by iPhoneDeveloper

  In object-oriented programming, there is no exact rule on the maximum length of a method , but I still found these two qutes somewhat contradicting each other, so I would like to hear what you think. In Clean Code: A Handbook of Agile Software Craftsmanship, Robert Martin says: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long. and he gives an example from Java code he sees from Kent Beck: Every function in his program was just two, or three, or four lines long. Each was transparently obvious. Each told a story. And each led you to the next in a compelling order. That’s how short your functions should be! This sounds great, but on the other hand, in Code Complete, Steve McConnell says something very different: The routine should be allowed to grow organically up to 100-200 lines, decades of evidence say that routines of such length no more error prone then shorter routines. And he gives a reference to a study that says routines 65 lines or long are cheaper to develop. So while there are diverging opinions about the matter, is there a functional best-practice towards determining the ideal length of a method for you?

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• What are known approaches to graphing algebraic expressions?

  - by jeremynealbrown

  I am planning to build an expression parser that will be used to graph algebraic functions ( think TI-83 ) with JavaScript. Functions will take the form of f(x)= Aside from typical operators such as: + - * / ^ I'd also like to add support for inline functions such as: sin(), cos(), log() and random(). I have looked at implementing the Shunting Yard algorithm for parsing expressions, but it does not look like an efficient approach to evaluating a function with a hundreds or thousands of inputs. What other known algorithms exist for this task?

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• CommonFilter and CommonData solutions on CodePlex updated

  - by TATWORTH

  The CommonFilter and CommonData solutions on Codeplex have been updated post VS2010 SP1. The respective URLs are: http://commondata.codeplex.com/releases/view/62502 http://commonfilter.codeplex.com/releases/view/62499 CommonFilter is a cut-down version of CommonData containing just the filter functions. Common Data contains a vast number of useful functions for building ASP.NET web sites including: Lightweight reporting to a custome event log Filter functions for common types of data input

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• Why is JavaScript not used for classical application development (compiled software)?

  - by Jose Faeti

  During my years of web development with JavaScript, I come to the conclusion that it's an incredible powerful language, and you can do amazing things with it. It offers a rich set of features, like: Dynamic typing First-class functions Nested functions Closures Functions as methods Functions as Object constructors Prototype-based Objects-based (almost everything is an object) Regex Array and Object literals It seems to me that almost everything can be achieved with this kind of language, you can also emulate OO programming, since it provides great freedom and many different coding styles. With more software-oriented custom functionalities (I/O, FileSystem, Input devices, etc.) I think it will be great to develop applications with. Though, as far as I know, it's only used in web development or in existing softwares as a scripting language only. Only recently, maybe thanks to the V8 Engine, it's been used more for other kind of tasks (see node.js for example). Why until now it's only be relegated only to web development? What is keeping it away from software development?

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• Is return-type-(only)-polymorphism in Haskell a good thing?

  - by dainichi

  One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a where foo::Int -> a Some of the reasons that I do not like this: Referential transparency: "In Haskell, given the same input, a function will always return the same output", but is that really true? read "3" return 3 when used in an Int context, but throws an error when used in a, say, (Int,Int) context. Yes, you can argue that read is also taking a type parameter, but the implicitness of the type parameter makes it lose some of its beauty in my opinion. Monomorphism restriction: One of the most annoying things about Haskell. Correct me if I'm wrong, but the whole reason for the MR is that computation that looks shared might not be because the type parameter is implicit. Type defaulting: Again one of the most annoying things about Haskell. Happens e.g. if you pass the result of functions polymorphic in their output to functions polymorphic in their input. Again, correct me if I'm wrong, but this would not be necessary without functions whose return type cannot be determined by their input type (and polymorphic constants). So my question is (running the risk of being stamped as a "discussion quesion"): Would it be possible to create a Haskell-like language where the type checker disallows these kinds of definitions? If so, what would be the benefits/disadvantages of that restriction? I can see some immediate problems: If, say, 2 only had the type Integer, 2/3 wouldn't type check anymore with the current definition of /. But in this case, I think type classes with functional dependencies could come to the rescue (yes, I know that this is an extension). Furthermore, I think it is a lot more intuitive to have functions that can take different input types, than to have functions that are restricted in their input types, but we just pass polymorphic values to them. The typing of values like [] and Nothing seems to me like a tougher nut to crack. I haven't thought of a good way to handle them. I doubt I am the first person to have had thoughts like these. Does anybody have links to good discussions about this Haskell design decision and the pros/cons of it?

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• Using lambdas for WPF animation

  Shows how to use lambdas and higher-order functions for WPF graphics work

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• Focusing and Selecting the Text in ASP.NET TextBox Controls

  When a browser displays the HTML sent from a web server it parses the received markup into a Document Object Model, or DOM, which models the markup as a hierarchical structure. Each element in the markup - the <form> element, <div> elements, <p> elements, <input> elements, and so on - are represented as a node in the DOM and can be programmatically accessed from client-side script. What's more, the nodes that make up the DOM have functions that can be called to perform certain behaviors; what functions are available depend on what type of element the node represents. One function common to most all node types is focus, which gives keyboard focus to the corresponding element. The focus function is commonly used in data entry forms, search pages, and login screens to put the user's keyboard cursor in a particular textbox when the web page loads so that the user can start typing in his search query or username without having to first click the textbox with his mouse. Another useful function is select, which is available for <input> and <textarea> elements and selects the contents of the textbox. This article shows how to call an HTML element's focus and select functions. We'll look at calling these functions directly from client-side script as well as how to call these functions from server-side code. Read on to learn more! Read More >

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• Help me sort programing languages a bit

  - by b-gen-jack-o-neill

  Hi, so I asked here few days ago about C# and its principles. Now, if I may, I have some additional general questions about some languages, becouse for novice like me, it seems a bit confusing. To be exact I want to ask more about language functions capabilities than syntax and so. To be honest, its just these special functions that bothers me and make me so confused. For exmaple, C has its printf(), Pascal has writeln() and so. I know in basic the output in assembler of these funtions would be similiar, every language has more or less its special functions. For console output, for file manipulation, etc. But all these functions are de-facto part of its OS API, so why is for example in C distinguished between C standard library functions and (on Windows) WinAPI functions when even printf() has to use some Windows feature, call some of its function to actually show desired text on console window, becouse the actuall "showing" is done by OS. Where is the line between language functions and system API? Now languages I dont quite understand - Python, Ruby and similiar. To be more specific, I know they are similiar to java and C# in term they are compiled into bytecode. But, I do not unerstand what are its capabilities in term of building GUI applications. I saw tutorial for using Ruby to program GUI applications on Linux and Windows. But isn´t that just some kind of upgrade? I mean fram other tutorials It seemed like these languages was first intended for small scripts than building big applications. I hope you understand why I am confused. If you do, please help me sort it out a bit, I have no one to ask.

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• How to map string keys to unique integer IDs?

  - by Marek

  I have some data that comes regularily as a dump from a data souce with a string natural key that is long (up to 60 characters) and not relevant to the end user. I am using this key in a url. This makes urls too long and user unfriendly. I would like to transform the string keys into integers with the following requirements: The source dataset will change over time. The ID should be: non negative integer unique and constant even if the set of input keys changes preferrably reversible back to key (not a strong requirement) The database is rebuilt from scratch every time so I can not remember the already assigned IDs and match the new data set to existing IDs and generate sequential IDs for the added keys. There are currently around 30000 distinct keys and the set is constantly growing. How to implement a function that will map string keys to integer IDs? What I have thought about: 1. Built-in string.GetHashCode: ID(key) = Math.Abs(key.GetHashCode()) is not guaranteed to be unique (not reversible) 1.1 "Re-hashing" the built-in GetHashCode until a unique ID is generated to prevent collisions. existing IDs may change if something colliding is added to the beginning of the input data set 2. a perfect hashing function I am not sure if this can generate constant IDs if the set of inputs changes (not reversible) 3. translate to base 36/64/?? does not shorten the long keys enough What are the other options?

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• Extraneous Library Linkage

  - by gmatt

  I have a question which may be somewhat silly because I'm pretty sure I may know the answer already. Suppose you have static library A, and dynamic shared object library B and your program C under linux. Suppose that library A calls functions from library B and your program calls functions from library A. Now suppose that all functions that C calls in A make no use of functions in B. To compile C will it be enough to link just A and omit B and furthermore can your program C be run on a system without library B installed?

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• Good practice of using list of function in Python

  - by riskio

  I am pretty new to python and I discovered by myself that I can create a list of function and call with a for loop. example: def a(args): print "A" def b(args): print "B" def c(args): print "C " + str(args) functions = [a,b,c] for i in functions: i(1) So, my question is: is there any good practice or elegant way to use list of functions and what is a good use of all this? (do have a particular name the "list of functions"?) thank you

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• What's the best way to handle modules that use each other?

  - by Axeman

  What's the best way to handle modules that use each other? Let's say I have a module which has functions for hashes: # Really::Useful::Functions::On::Hash.pm use base qw<Exporter>; use strict; use warnings; use Really::Useful::Functions::On::List qw<transform_list>; our @EXPORT_OK = qw<transform_hash transform_hash_as_list ...>; #... sub transform_hash { ... } #... sub transform_hash_as_list { return transform_list( %{ shift() } ); } #... 1 And another module has been segmented out for lists: # Really::Useful::Functions::On::List.pm use base qw<Exporter>; use strict; use warnings; use Really::Useful::Functions::On::Hash qw<transform_hash>; our @EXPORT_OK = qw<transform_list some_func ...>; #... sub transform_list { ... } #... sub some_func { my %params = transform_hash @_; #... } #... 1 Suppose that enough of these utility functions are handy enough that I'll want to use them in BEGIN statements and import functions to process parameter lists or configuration data. I have been putting sub definitions into BEGIN blocks to make sure they are ready to use whenever somebody includes the module. But I have gotten into hairy race conditions where a definition is not completed in a BEGIN block. I put evolving code idioms into modules so that I can reuse any idiom I find myself coding over and over again. For instance: sub list_if { my $condition = shift; return unless $condition; my $more_args = scalar @_; my $arg_list = @_ > 1 ? \@_ : @_ ? shift : $condition; if (( reftype( $arg_list ) || '' ) eq 'ARRAY' ) { return wantarray ? @$arg_list : $arg_list; } elsif ( $more_args ) { return $arg_list; } return; } captures two idioms that I'm kind of tired of typing: @{ func_I_hope_returns_a_listref() || [] } and ( $condition ? LIST : ()) The more I define functions in BEGIN blocks, the more likely I'll use these idiom bricks to express the logic the more likely that bricks are needed in BEGIN blocks. Do people have standard ways of dealing with this sort of language-idiom-brick model? I've been doing mostly Pure-Perl; will XS alleviate some of this?

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• Hash Functions. Commonly used method h(k) = k mod M,, Why we choose value of M to be prime no.

  - by RBA

  Hi, Please share the reason why in Hash Functions, the common method i.e. h(k) = k mod M... Why we choose the value of M to be always prime no. Thanks..

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• Haskell mutability in compiled state?

  - by pile of junk

  I do not know much about Haskell, but from what I have read about the mutability of computations (e.g: functions returning functions, complex monads and functions, etc.) it seems like you can do a lot of meta-programming, even at runtime. How can Haskell, if everything like functions and monads are so complex, compile to machine code and retain all this?

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• Yii include PHP Excel

  - by Anton Sementsov

  Im trying include PHPExcel lib to Yii, put PHPExcel.php in root of extensions, near PHPExcel folder and added that code into config/main.php // application components 'components'=>array( 'excel'=>array( 'class'=>'application.extensions.PHPExcel', ), modify /protected/extensions/PHPExcel/Autoloader.php public static function Register() { $functions = spl_autoload_functions(); foreach($functions as $function) spl_autoload_unregister($function); $functions=array_merge(array(array('PHPExcel_Autoloader', 'Load')), $functions); foreach($functions as $function) $x = spl_autoload_register($function); return $x; }// function Register() Then, trying create PHPExcel object $objPHPExcel = new PHPExcel(); but have an error: include(PHPExcel.php) [<a href='function.include'>function.include</a>]: failed to open stream: No such file or directory in Z:\home\yii.local\www\framework\YiiBase.php(418)

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• Best code structure for arcade games

  - by user280454

  Hi, I've developed a few arcade games so far and have the following structure in almost all of them: I have 1 file which contains a class called kernel with the following functions: init() welcome_screen() menu_screen() help_Screen() play_game() end_screen() And another file, called Game, which basically calls all these functions and controls the flow of the game. Also, I have classes for different characters, whenever required. Is this a good code structure, or should I try having different files(classes) for different functions like welcome screen, playing, help screen, etc? As in, instead of including all the code for these things in 1 file, should I be having different classes for each one of them? The only problem I think it might cause is that I would need certain variables like score, characters, etc which are common to all of them, that's why I have all these functions in a Kernel class so that all these functions can use these variables.

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• weird data-grid-view/crystal-reports behaviour c# winforms

  - by jello

  I have a winforms project which I keep in different versions, each version having its own project folder. All these projects use the same database file, which is copied in each project folder too. So if I run a project, let's say 0.34, and then I try to run 0.35, all the database functions don't work, unless I detach the database in SQL server management studio express. So all the database functions don't work, except the data grid view and/or crystal reports. But then, if I detach the database, and I run any version, all the database functions work, except the data grid view and/or crystal reports. So to recap, when the database functions work (like select), crystal reports doesn't work. But when the database functions don't work because the database is not detached, crystal reports works. weird. any ideas?

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• Direct video card access

  - by icemanind

  Guys, I am trying to write a class in C# that can be used as a direct replacement for the C# Bitmap class. What I want to do instead though is perform all graphic functions done on the bitmap using the power of the video card. From what I understand, functions such as DrawLine or DrawArc or DrawText are primitive functions that use simple cpu math algorithms to perform the job. I, instead, want to use the graphics card cpu and memory to do these and other advanced functions, such as skinning a bitmap (applying a texture) and true transparancy. My problem is, in C#, how do I access direct video functions? Is there a library or something I need?

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• Usercontrol access javascript from a Content's Page's Master Page

  - by Coda

  Hello all I have a problem. I have a masterpage that all of my Content pages inherit from. Within this masterpage I have a script tag pointing to the javascript file folder "~/Scripts/validation.js" On my content pages I use different usercontrols that require the use of many of the functions within the validation.js file however if I dont put the tag and the javascript functions within a contentholder on the contentpage the usercontrols do not see these functions and I get errors like "OnNameValidation" is not defined. Of course I can copy the javscript code into all of the pages but that's 30+ pages and a maintenance nightmare if I find a bug in one of the javscript functions. So the question (if you haven't already figured out from my long dissertation) is how can I declare the script tag with the path to the validation.js file so that contentpages and their usercontrols etc. can access the functions/code. Thanks in advance.

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• Connecting to the database in a Created Library - CodeIgniter

  - by Brogrammer

  I have a little issue right now and its bugging me, hopefully one of you guys will be able to help me out. Basically I'm creating a library to use in CodeIgniter and I'm getting this error: A PHP Error was encountered Severity: Notice Message: Undefined property: Functions::$db Filename: libraries/Functions.php Line Number: 11 The Database library is already on autoload aswell as my functions library: $autoload['libraries'] = array('database','session','encrypt','functions'); The Functions.php file is located in the application/libraries folder accordingly. Line number 11 consists of this: $this->db->where('username', $data); Not sure as to why the db is an undefined property?

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• BizTalk Testing Series - The xpath Function

  - by Michael Stephenson

  Background While the xpath function in a BizTalk orchestration is a very powerful feature I have often come across the situation where someone has hard coded an xpath expression in an orchestration. If you have read some of my previous posts about testing I've tried to get across the general theme like test-driven or test-assisted development approaches where the underlying principle is that your building up your solution of small well tested units that are put together and the resulting solution is usually quite robust. You will be finding more bugs within your unit tests and fewer outside of your team. The thing I don't like about the xpath functions usual usage is when you come across an orchestration which has something like the below snippet in an expression or assign shape: string result = xpath(myMessage,"string(//Order/OrderItem/ProductName)"); My main issue with this is that the xpath statement is hard coded in the orchestration and you don't really know it works until you are running the orchestration. Some of the problems I think you end up with are: You waste time with lengthy debugging of the orchestration when your statement isn't working You might not know the function isn't working quite as expected because the testable unit around it is big You are much more open to regression issues if your schema changes     Approach to Testing The technique I usually follow is to hold the xpath statement as a constant in a helper class or to format a constant with a helper function to get the actual xpath statement. It is then used by the orchestration like follows. string result = xpath(myMessage, MyHelperClass.ProductNameXPathStatement); This means that because the xpath statement is available outside of the orchestration it now becomes testable in its own right. This means: I can test it in its own right I'm less likely to waste time tracking down problems caused by an error in the statement I can reduce the risk or regression issuess I'm now able to implement some testing around my xpath statements which usually are something like the following:    The test will use a sample xml file The sample will be validated against the schema The test will execute the xpath statement and then check the results are as expected     Walk-through BizTalk uses the XPathNavigator internally behind the xpath function to implement the queries you will usually use using the navigators select or evaluate functions. In the sample (link at bottom) I have a small solution which contains a schema from which I have generated a sample instance. I will then use this instance as the basis for my tests.     In the below diagram you can see the helper class which I've encapsulated my xpath expressions in, and some helper functions which will format the expression in the case of a repeating node which would want to inject an index into the xpath query.             I have then created a test class which has some functions to execute some queries against my sample xml file. An example of this is below.         In the test class I have a couple of helper functions which will execute the xpath expressions in a similar way to BizTalk. You could have a proper helper class to do this if you wanted.         You can see now in the BizTalk expression editor I can use these functions alongside the xpath function.         Conclusion I hope you can see with very little effort you can make your life much easier by testing xpath statements outside of an orchestration rather than using them directly hard coded into the orchestration.     This can also save you lots of pain longer term because your build should break if your schema changes unexpectedly causing these xpath tests to fail where as your tests around the orchestration will be more difficult to troubleshoot and workout the cause of the problem.     Sample Link The sample is available from the following link: http://code.msdn.microsoft.com/testbtsxpathfunction     Other Tools On the subject of using the xpath function, if you don't already use it the below tool is very useful for creating your xpath statements (thanks BizBert) http://www.bizbert.com/bizbert/2007/11/30/XPath+The+Hidden+Language+Of+BizTalk.aspx

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• Asynchrony in C# 5 (Part I)

  - by javarg

  I’ve been playing around with the new Async CTP preview available for download from Microsoft. It’s amazing how language trends are influencing the evolution of Microsoft’s developing platform. Much effort is being done at language level today than previous versions of .NET. In these post series I’ll review some major features contained in this release: Asynchronous functions TPL Dataflow Task based asynchronous Pattern Part I: Asynchronous Functions This is a mean of expressing asynchronous operations. This kind of functions must return void or Task/Task<> (functions returning void let us implement Fire & Forget asynchronous operations). The two new keywords introduced are async and await. async: marks a function as asynchronous, indicating that some part of its execution may take place some time later (after the method call has returned). Thus, all async functions must include some kind of asynchronous operations. This keyword on its own does not make a function asynchronous thought, its nature depends on its implementation. await: allows us to define operations inside a function that will be awaited for continuation (more on this later). Async function sample: Async/Await Sample async void ShowDateTimeAsync() {     while (true)     {         var client = new ServiceReference1.Service1Client();         var dt = await client.GetDateTimeTaskAsync();         Console.WriteLine("Current DateTime is: {0}", dt);         await TaskEx.Delay(1000);     } } The previous sample is a typical usage scenario for these new features. Suppose we query some external Web Service to get data (in this case the current DateTime) and we do so at regular intervals in order to refresh user’s UI. Note the async and await functions working together. The ShowDateTimeAsync method indicate its asynchronous nature to the caller using the keyword async (that it may complete after returning control to its caller). The await keyword indicates the flow control of the method will continue executing asynchronously after client.GetDateTimeTaskAsync returns. The latter is the most important thing to understand about the behavior of this method and how this actually works. The flow control of the method will be reconstructed after any asynchronous operation completes (specified with the keyword await). This reconstruction of flow control is the real magic behind the scene and it is done by C#/VB compilers. Note how we didn’t use any of the regular existing async patterns and we’ve defined the method very much like a synchronous one. Now, compare the following code snippet  in contrast to the previuous async/await: Traditional UI Async void ComplicatedShowDateTime() {     var client = new ServiceReference1.Service1Client();     client.GetDateTimeCompleted += (s, e) =>     {         Console.WriteLine("Current DateTime is: {0}", e.Result);         client.GetDateTimeAsync();     };     client.GetDateTimeAsync(); } The previous implementation is somehow similar to the first shown, but more complicated. Note how the while loop is implemented as a chained callback to the same method (client.GetDateTimeAsync) inside the event handler (please, do not do this in your own application, this is just an example).  How it works? Using an state workflow (or jump table actually), the compiler expands our code and create the necessary steps to execute it, resuming pending operations after any asynchronous one. The intention of the new Async/Await pattern is to let us think and code as we normally do when designing and algorithm. It also allows us to preserve the logical flow control of the program (without using any tricky coding patterns to accomplish this). The compiler will then create the necessary workflow to execute operations as the happen in time.

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