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  • What triggered the popularity of lambda functions in modern mainstream programming languages?

    - by Giorgio
    In the last few years anonymous functions (AKA lambda functions) have become a very popular language construct and almost every major / mainstream programming language has introduced them or is planned to introduce them in an upcoming revision of the standard. Yet, anonymous functions are a very old and very well-known concept in Mathematics and Computer Science (invented by the mathematician Alonzo Church around 1936, and used by the Lisp programming language since 1958, see e.g. here). So why didn't today's mainstream programming languages (many of which originated 15 to 20 years ago) support lambda functions from the very beginning and only introduced them later? And what triggered the massive adoption of anonymous functions in the last few years? Is there some specific event, new requirement or programming technique that started this phenomenon? IMPORTANT NOTE The focus of this question is the introduction of anonymous functions in modern, main-stream (and therefore, maybe with a few exceptions, non functional) languages. Also, note that anonymous functions (blocks) are present in Smalltalk, which is not a functional language, and that normal named functions have been present even in procedural languages like C and Pascal for a long time. Please do not overgeneralize your answers by speaking about "the adoption of the functional paradigm and its benefits", because this is not the topic of the question.

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  • What do you mean by the expressiveness in a programming language?

    - by prosseek
    I see a lot of the word 'expressiveness' when people want to stress one language is better than the other. But I don't see exactly what they mean by it. Is it the verboseness/succinctness? I mean, if one language can write down something shorter than the other, does that mean expressiveness? Please refer to my other question - http://stackoverflow.com/questions/2411772/article-about-code-density-as-a-measure-of-programming-language-power Is it the power of the language? Paul Graham says that one language is more powerful than the other language in a sense that one language can do that the other language can't do (for example, LISP can do something with macro that the other language can't do). Is it just something that makes life easier? Regular expression can be one of the examples. Is it a different way of solving the same problem: something like SQL to solve the search problem? What do you think about the expressiveness of a programming language? Can you show the expressiveness using some code? What's the relationship with the expressiveness and DSL? Do people come up with DSL to get the expressiveness?

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  • What do you mean by the expressiveness in programming lanuguage?

    - by prosseek
    I see a lot of the word 'expressiveness' when people want to stress one language is better than the other. But I don't see exactly what they mean by it. Is it the verboseness/succinctness? I mean, if one language can write down something shorter than the other, does that mean expressiveness? Please refer to my other question - http://stackoverflow.com/questions/2411772/article-about-code-density-as-a-measure-of-programming-language-power Is it the power of the language? Paul Graham says that one language is more powerful than the other language in a sense that one language can do that the other language can't do (for example, LISP can do something with macro that the other language can't do). Is it just something that makes life easier? Regular expression can be one of the examples. Is it a different way of solving the same problem: something like SQL to solve the search problem? What do you think about the expressiveness of a programming lanuage? Can you show the expressiveness using some code? What's the relationship with the expressiveness and DSL? Do people come up with DSL to get the expressiveness?

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  • Creating a dynamic proxy generator with c# – Part 4 – Calling the base method

    - by SeanMcAlinden
    Creating a dynamic proxy generator with c# – Part 1 – Creating the Assembly builder, Module builder and caching mechanism Creating a dynamic proxy generator with c# – Part 2 – Interceptor Design Creating a dynamic proxy generator with c# – Part 3 – Creating the constructors   The plan for calling the base methods from the proxy is to create a private method for each overridden proxy method, this will allow the proxy to use a delegate to simply invoke the private method when required. Quite a few helper classes have been created to make this possible so as usual I would suggest download or viewing the code at http://rapidioc.codeplex.com/. In this post I’m just going to cover the main points for when creating methods. Getting the methods to override The first two notable methods are for getting the methods. private static MethodInfo[] GetMethodsToOverride<TBase>() where TBase : class {     return typeof(TBase).GetMethods().Where(x =>         !methodsToIgnore.Contains(x.Name) &&                              (x.Attributes & MethodAttributes.Final) == 0)         .ToArray(); } private static StringCollection GetMethodsToIgnore() {     return new StringCollection()     {         "ToString",         "GetHashCode",         "Equals",         "GetType"     }; } The GetMethodsToIgnore method string collection contains an array of methods that I don’t want to override. In the GetMethodsToOverride method, you’ll notice a binary AND which is basically saying not to include any methods marked final i.e. not virtual. Creating the MethodInfo for calling the base method This method should hopefully be fairly easy to follow, it’s only function is to create a MethodInfo which points to the correct base method, and with the correct parameters. private static MethodInfo CreateCallBaseMethodInfo<TBase>(MethodInfo method) where TBase : class {     Type[] baseMethodParameterTypes = ParameterHelper.GetParameterTypes(method, method.GetParameters());       return typeof(TBase).GetMethod(        method.Name,        BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic,        null,        baseMethodParameterTypes,        null     ); }   /// <summary> /// Get the parameter types. /// </summary> /// <param name="method">The method.</param> /// <param name="parameters">The parameters.</param> public static Type[] GetParameterTypes(MethodInfo method, ParameterInfo[] parameters) {     Type[] parameterTypesList = Type.EmptyTypes;       if (parameters.Length > 0)     {         parameterTypesList = CreateParametersList(parameters);     }     return parameterTypesList; }   Creating the new private methods for calling the base method The following method outline how I’ve created the private methods for calling the base class method. private static MethodBuilder CreateCallBaseMethodBuilder(TypeBuilder typeBuilder, MethodInfo method) {     string callBaseSuffix = "GetBaseMethod";       if (method.IsGenericMethod || method.IsGenericMethodDefinition)     {                         return MethodHelper.SetUpGenericMethod             (                 typeBuilder,                 method,                 method.Name + callBaseSuffix,                 MethodAttributes.Private | MethodAttributes.HideBySig             );     }     else     {         return MethodHelper.SetupNonGenericMethod             (                 typeBuilder,                 method,                 method.Name + callBaseSuffix,                 MethodAttributes.Private | MethodAttributes.HideBySig             );     } } The CreateCallBaseMethodBuilder is the entry point method for creating the call base method. I’ve added a suffix to the base classes method name to keep it unique. Non Generic Methods Creating a non generic method is fairly simple public static MethodBuilder SetupNonGenericMethod(     TypeBuilder typeBuilder,     MethodInfo method,     string methodName,     MethodAttributes methodAttributes) {     ParameterInfo[] parameters = method.GetParameters();       Type[] parameterTypes = ParameterHelper.GetParameterTypes(method, parameters);       Type returnType = method.ReturnType;       MethodBuilder methodBuilder = CreateMethodBuilder         (             typeBuilder,             method,             methodName,             methodAttributes,             parameterTypes,             returnType         );       ParameterHelper.SetUpParameters(parameterTypes, parameters, methodBuilder);       return methodBuilder; }   private static MethodBuilder CreateMethodBuilder (     TypeBuilder typeBuilder,     MethodInfo method,     string methodName,     MethodAttributes methodAttributes,     Type[] parameterTypes,     Type returnType ) { MethodBuilder methodBuilder = typeBuilder.DefineMethod(methodName, methodAttributes, returnType, parameterTypes); return methodBuilder; } As you can see, you simply have to declare a method builder, get the parameter types, and set the method attributes you want.   Generic Methods Creating generic methods takes a little bit more work. /// <summary> /// Sets up generic method. /// </summary> /// <param name="typeBuilder">The type builder.</param> /// <param name="method">The method.</param> /// <param name="methodName">Name of the method.</param> /// <param name="methodAttributes">The method attributes.</param> public static MethodBuilder SetUpGenericMethod     (         TypeBuilder typeBuilder,         MethodInfo method,         string methodName,         MethodAttributes methodAttributes     ) {     ParameterInfo[] parameters = method.GetParameters();       Type[] parameterTypes = ParameterHelper.GetParameterTypes(method, parameters);       MethodBuilder methodBuilder = typeBuilder.DefineMethod(methodName,         methodAttributes);       Type[] genericArguments = method.GetGenericArguments();       GenericTypeParameterBuilder[] genericTypeParameters =         GetGenericTypeParameters(methodBuilder, genericArguments);       ParameterHelper.SetUpParameterConstraints(parameterTypes, genericTypeParameters);       SetUpReturnType(method, methodBuilder, genericTypeParameters);       if (method.IsGenericMethod)     {         methodBuilder.MakeGenericMethod(genericArguments);     }       ParameterHelper.SetUpParameters(parameterTypes, parameters, methodBuilder);       return methodBuilder; }   private static GenericTypeParameterBuilder[] GetGenericTypeParameters     (         MethodBuilder methodBuilder,         Type[] genericArguments     ) {     return methodBuilder.DefineGenericParameters(GenericsHelper.GetArgumentNames(genericArguments)); }   private static void SetUpReturnType(MethodInfo method, MethodBuilder methodBuilder, GenericTypeParameterBuilder[] genericTypeParameters) {     if (method.IsGenericMethodDefinition)     {         SetUpGenericDefinitionReturnType(method, methodBuilder, genericTypeParameters);     }     else     {         methodBuilder.SetReturnType(method.ReturnType);     } }   private static void SetUpGenericDefinitionReturnType(MethodInfo method, MethodBuilder methodBuilder, GenericTypeParameterBuilder[] genericTypeParameters) {     if (method.ReturnType == null)     {         methodBuilder.SetReturnType(typeof(void));     }     else if (method.ReturnType.IsGenericType)     {         methodBuilder.SetReturnType(genericTypeParameters.Where             (x => x.Name == method.ReturnType.Name).First());     }     else     {         methodBuilder.SetReturnType(method.ReturnType);     }             } Ok, there are a few helper methods missing, basically there is way to much code to put in this post, take a look at the code at http://rapidioc.codeplex.com/ to follow it through completely. Basically though, when dealing with generics there is extra work to do in terms of getting the generic argument types setting up any generic parameter constraints setting up the return type setting up the method as a generic All of the information is easy to get via reflection from the MethodInfo.   Emitting the new private method Emitting the new private method is relatively simple as it’s only function is calling the base method and returning a result if the return type is not void. ILGenerator il = privateMethodBuilder.GetILGenerator();   EmitCallBaseMethod(method, callBaseMethod, il);   private static void EmitCallBaseMethod(MethodInfo method, MethodInfo callBaseMethod, ILGenerator il) {     int privateParameterCount = method.GetParameters().Length;       il.Emit(OpCodes.Ldarg_0);       if (privateParameterCount > 0)     {         for (int arg = 0; arg < privateParameterCount; arg++)         {             il.Emit(OpCodes.Ldarg_S, arg + 1);         }     }       il.Emit(OpCodes.Call, callBaseMethod);       il.Emit(OpCodes.Ret); } So in the main method building method, an ILGenerator is created from the method builder. The ILGenerator performs the following actions: Load the class (this) onto the stack using the hidden argument Ldarg_0. Create an argument on the stack for each of the method parameters (starting at 1 because 0 is the hidden argument) Call the base method using the Opcodes.Call code and the MethodInfo we created earlier. Call return on the method   Conclusion Now we have the private methods prepared for calling the base method, we have reached the last of the relatively easy part of the proxy building. Hopefully, it hasn’t been too hard to follow so far, there is a lot of code so I haven’t been able to post it all so please check it out at http://rapidioc.codeplex.com/. The next section should be up fairly soon, it’s going to cover creating the delegates for calling the private methods created in this post.   Kind Regards, Sean.

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  • How to determine if a programming language is verbose or terse?

    - by sunpech
    Programming languages can often be described as verbose or terse. From my understanding, a verbose language is easy to read and understand, while a terse language is concise and neat, but more difficult to read. Should there be other things to consider in the definitions? It seems much of the popular programming languages of today are verbose, and these terms two terms are only used to describe a language as being more or less, relative to than another language. How do we determine if a programming language is more verbose/terse over another? Example: Is C# more verbose than Java?

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  • What are the options for setting up a UNIX environment to learn C using Kernighan and Richie's The C Programming Language?

    - by ssbrewster
    I'm a novice programmer and have been experimenting with Javascript, jQuery and PHP but felt I wasn't getting a real depth of understanding of what I was doing. So, after reading Joel Spolsky's response to a question on this site (which I can't find now!), I took it back to basics and read Charles Petzold's 'Code' and am about to move onto Kernighan and Richie's The C Programming Language. I want to learn this in a UNIX environment but only have access to a Windows system. I have Ubuntu 12.04 running on a virtualised machine via VMWare Player, and done some coding in the terminal. Is using a Linux distro the only option for programming in a UNIX environment on Windows? And what are the next steps to start programming in C in UNIX and where do I get a compiler from?

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  • Stupid Geek Tricks: 6 Ways to Open Windows Task Manager

    - by Patrick Bisch
    Bringing up Windows Task Manager is not much of a task itself, but when a virus disables Ctrl+Alt+Del and takes it hostage, how else are you going to open task manager? Or maybe you’re just looking for some diversity in your life, so here are 6 different ways to open Windows Task Manager.HTG Explains: Photography with Film-Based CamerasHow to Clean Your Dirty Smartphone (Without Breaking Something)What is a Histogram, and How Can I Use it to Improve My Photos?

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  • What would you do if your client required you not to use object-oriented programming?

    - by gunbuster363
    Would you try to persuade your client that using object-oriented programming is much cleaner? Or would you try to follow what he required and give him crappy code? Now I am writing a program to simulate the activity of ants in a grid. The ant can move around, pick up things and drop things. The problem is while the action of the ants and the positions of each ant can be tracked by class attributes easily (and we can easily create many instances of such ants) my client said that since he has a background in functional programming he would like the simulation to be made using functional programming. What would you do?

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  • Have you used the ExecutionValue and ExecValueVariable properties?

    The ExecutionValue execution value property and it’s friend ExecValueVariable are a much undervalued feature of SSIS, and many people I talk to are not even aware of their existence, so I thought I’d try and raise their profile a bit. The ExecutionValue property is defined on the base object Task, so all tasks have it available, but it is up to the task developer to do something useful with it. The basic idea behind it is that it allows the task to return something useful and interesting about what it has performed, in addition to the standard success or failure result. The best example perhaps is the Execute SQL Task which uses the ExecutionValue property to return the number of rows affected by the SQL statement(s). This is a very useful feature, something people often want to capture into a variable, and start using the result set options to do. Unfortunately we cannot read the value of a task property at runtime from within a SSIS package, so the ExecutionValue property on its own is a bit of a let down, but enter the ExecValueVariable and we have the perfect marriage. The ExecValueVariable is another property exposed through the task (TaskHost), which lets us select a SSIS package variable. What happens now is that when the task sets the ExecutionValue, the interesting value is copied into the variable we set on the ExecValueVariable property, and a variable is something we can access and do something with. So put simply if the ExecutionValue property value is of interest, make sure you create yourself a package variable and set the name as the ExecValueVariable. Have  look at the 3 step guide below: 1 Configure your task as normal, for example the Execute SQL Task, which here calls a stored procedure to do some updates. 2 Create variable of a suitable type to match the ExecutionValue, an integer is used to match the result we want to capture, the number of rows. 3 Set the ExecValueVariable for the task, just select the variable we created in step 2. You need to do this in Properties grid for the task (Short-cut key, select the task and press F4) Now when we execute the sample task above, our variable UpdateQueueRowCount will get the number of rows we updated in our Execute SQL Task. I’ve tried to collate a list of tasks that return something useful via the ExecutionValue and ExecValueVariable mechanism, but the documentation isn’t always great. Task ExecutionValue Description Execute SQL Task Returns the number of rows affected by the SQL statement or statements. File System Task Returns the number of successful operations performed by the task. File Watcher Task Returns the full path of the file found Transfer Error Messages Task Returns the number of error messages that have been transferred Transfer Jobs Task Returns the number of jobs that are transferred Transfer Logins Task Returns the number of logins transferred Transfer Master Stored Procedures Task Returns the number of stored procedures transferred Transfer SQL Server Objects Task Returns the number of objects transferred WMI Data Reader Task Returns an object that contains the results of the task. Not exactly clear, but I assume it depends on the WMI query used.

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  • generic programming- where did it originate?

    - by user997112
    Im trying to work out if generic programming was a functional programming feature which was then introduced into Java, C++ and C# or did the latter copy it from the functional programming languages like Haskell, Lisp, OCaml etc? Google is giving me lots on what generic programming is, but not where it originated. All I can see is that Ada implemented it early on. Would you class it as a functional programming technique?

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  • Is programming for me? It seems too rigid and unforgiving.

    - by AM
    This question is a follow-up to: Should I continue to pursue programming based on my experience? I am currently majoring in CS in college and was thinking along similar lines as the above question. I'm fine at math and logic, but I haven't yet found programming to be enjoyable. Although I like the idea of being able to build software, too much of it seems to consist of figuring out tiny details or dealing with annoying bugs. So far I've only done small school projects and the like. Does programming become more enjoyable once you have more experience? How can someone know if a career in it is for them?

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  • How to deal with the need to know multiple programming languages? When to stop learning new languages?

    - by Raphael
    I am a relatively young programmer. I am 23 and I have been programming professionally for about 5 years. As most programmers I started with C, learned some x86 assembly for fun and then I found C++ which turned out to be my greatest passion in the programming world. Programming with C and C++ forces you to learn platform specific APIs, libs and frameworks all of each requires constant study and experimentation. After some time I had to move on to Java and C# as the demand on my region is basically for these languages. With these languages I entered the world of web development and then I had to learn javascript. Developing for the .NET Framework was exciting at first but I constantly felt as I was getting tied up by Microsoft (and of course the .NET Framework was driving me away from Linux). For desktop development I could do pretty much everything I did with .NET using C++ with Qt but for web development I had to look for an alternative. Quickly I found Django and then I proceeded to learn Python so I could use Django. Nowadays I am learning iOS development with Objective-C. So far it was pretty much easy to learn all these languages (C++ trained me well) but I am worried that someday I won't be able to keep track of them all. Just to clarify. The only languages I learned cause I had to were C# and Java. All of the others I learned for fun, because I love programming and learning new things. Also I like to keep my skills sharp on desktop, web and mobile development. My question is: How do you keep track of multiple programming languages? (I mean, keep track of changes to these languages and keep your skills sharp) and: Is there such a thing as enough programming languages?

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  • Why hasn't functional programming taken over yet?

    - by pankrax
    I've read some texts about declarative/functional programming (languages), tried out Haskell as well as written one myself. From what I've seen, functional programming has several advantages over the classical imperative style: Stateless programs; No side effects Concurrency; Plays extremely nice with the rising multi-core technology Programs are usually shorter and in some cases easier to read Productivity goes up (example: Erlang) Imperative programming is a very old paradigm (as far as I know) and possibly not suitable for the 21st century Why are companies using or programs written in functional languages still so "rare"? Why, when looking at the advantages of functional programming, are we still using imperative programming languages? Maybe it was too early for it in 1990, but today?

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  • Execute Ant task with Maven

    - by Gonzalo
    Hi, I'm trying to execute with Maven some test written using Ant tasks. I generated the files required to import the task into Maven, but I can't execute them. My POM is defined this way: <build> <plugins> <plugin> <artifactId>maven-ant-plugin</artifactId> <version>2.1</version> <executions> <execution> <phase>generate-sources</phase> <configuration> <tasks> <echo message="Hello, maven"/> </tasks> </configuration> <goals> <goal>run</goal> </goals> </execution> </executions> </plugin> </plugins> </build> I try to execute that message, but I get an error with run: [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] 'run' was specified in an execution, but not found in the plugin But, if I run: "mvn antrun:run", I know that this can not run the task. An if I've different targets, how do I call them from Maven? I've the pom.xml, and build.xml with the ant tasks. Thanks. Gonzalo

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  • Maven build fails on an Ant FTP task failure

    - by fraido
    I'm using the FTP Ant task with maven-antrun-plugin <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-antrun-plugin</artifactId> <executions> <execution> <id>ftp</id> <phase>generate-resources</phase> <configuration> <tasks> <ftp action="get" server="${ftp.server.ip}" userid="${ftp.server.userid}" password="${ftp.server.password}" remotedir="${ftp.server.remotedir}" depends="yes" verbose="yes" skipFailedTransfers="true" ignoreNoncriticalErrors="true"> <fileset dir="target/test-classes/testdata"> <include name="**/*.html" /> </fileset> </ftp> </tasks> </configuration> <goals> <goal>run</goal> </goals> </execution> </executions> ... the problem is that my build fails when the folder ${ftp.server.remotedir} doesn't exist. I tried to specify skipFailedTransfers="true" ignoreNoncriticalErrors="true but these don't fix the problem and the build keeps failing. An Ant BuildException has occured: could not change remote directory: 550 /myBadDir: The system cannot find the file specified. Do you know how to instruct my maven build to don't care about this Ant task error

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  • Task Manager: CPU usage history

    - by Nezdet
    I bougth recently a server with 2 x X5550, they are quad (4 cores each) total 8 cores If I check the task manager it shows in the CPU usage history 16 diagrams, Should't it be 8 cause I have 2 processors with quad? or the diagrams maybee shows the Threads of the CPU?

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  • Custom Task Queue in App Engine?

    - by demos
    I have created a new task queue and defined it in queue.yaml I am not sure how to start adding tasks to this queue? with the default queue it is simple taskqueue.add(...) how do we do it for a custom queue?

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  • base for setQueueXmlPath

    - by antony.trupe
    I can't figure out how to point unit tests at the queue config file. Unit Test snippet // TaskQueue setup LocalTaskQueueTestConfig tqConfig = new LocalTaskQueueTestConfig(); tqConfig.setQueueXmlPath("/war/WEB_INF/queue.xml"); Stack Trace java.lang.IllegalStateException: The specified queue is unknown : zip-fetch at com.google.appengine.api.labs.taskqueue.QueueApiHelper.translateError(QueueApiHelper.java:56) at com.google.appengine.api.labs.taskqueue.QueueApiHelper.translateError(QueueApiHelper.java:111) at com.google.appengine.api.labs.taskqueue.QueueApiHelper.makeSyncCall(QueueApiHelper.java:32) at com.google.appengine.api.labs.taskqueue.QueueImpl.add(QueueImpl.java:310) at com.google.appengine.api.labs.taskqueue.QueueImpl.add(QueueImpl.java:282) at com.google.appengine.api.labs.taskqueue.QueueImpl.add(QueueImpl.java:267) at ...

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  • Task Queue Java API

    - by user268515
    Hi when i started to work on Task queue concept i got struck on this line queue.add( DatastoreServiceFactory.getDatastoreService().getCurrentTransaction(), TaskOptions().url("/path/to/my/worker")); What will DatastoreServiceFactory do... How to redirect this page to another servlet.... in the url i gave .url("/myservlet") but it doesn't redirected to servlet Please say what should given in .url.Help me. Regards, sharun

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  • Is there a programming language that performs currying when named parameters are omitted?

    - by Adam Gent
    Many functional programming languages have support for curried parameters. To support currying functions the parameters to the function are essentially a tuple where the last parameter can be omitted making a new function requiring a smaller tuple. I'm thinking of designing a language that always uses records (aka named parameters) for function parameters. Thus simple math functions in my make believe language would be: add { left : num, right : num } = ... minus { left : num, right : num } = .. You can pass in any record to those functions so long as they have those two named parameters (they can have more just "left" and "right"). If they have only one of the named parameter it creates a new function: minus5 :: { left : num } -> num minus5 = minus { right : 5 } I borrow some of haskell's notation for above. Has any one seen a language that does this?

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  • Task Manager Like App using Java Swing

    - by buddhika
    I want to how know how to set about writing a monitoring app such as Windows task manager using Java Swing. The main feature I am concerned with is the grid with a graph which get drawn with time. What are the features that I need to accomplish this? (e.g.: Java2D etc).

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