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• What kind of knowledge you need to invent a new programming language?

  - by systempuntoout

  I just finished to read "coders at works", a brilliant book by Peter Seibel with 15 interviews to some of the most interesting computer programmers alive today. Well, many of the interviewees have (co)invented\implemented a new programming language. For example: * Joe Armstrong: Inventor of Erlang * L. Peter Deutsch: implementer of Smalltalk-80 * Brendan Eich: Inventor of JavaScript * Dan Ingalls: Smalltalk implementor and designer * Simon Peyton Jones: Coinventor of Haskell * Guy Steele: Coinventor of Scheme Is out of any doubt that their minds have something special and unreachable, and i'm not crazy to think i will ever able to create a new language; i'm just interested in this topic. So, imagine a funny\grotesque scenario where your crazy boss one day will come to your desk to say "i want a new programming language with my name on it..take the time you need and do it", what will you start to study? What kind of knowledge do you need to model, design and implement a brand new programming language?

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• Are some data structures more suitable for functional programming than others?

  - by Rob Lachlan

  In Real World Haskell, there is a section titled "Life without arrays or hash tables" where the authors suggest that list and trees are preferred in functional programming, whereas an array or a hash table might be used instead in an imperative program. This makes sense, since it's much easier to reuse part of an (immutable) list or tree when creating a new one than to do so with an array. So my questions are: Are there really significantly different usage patterns for data structures between functional and imperative programming? If so, is this a problem? What if you really do need a hash table for some application? Do you simply swallow the extra expense incurred for modifications?

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• In what areas might the use of F# be more appropriate than C#?

  - by Peter McGrattan

  Over the last few years F# has evolved into one of Microsoft's fully supported languages employing many ideas incubated in OCaml, ML and Haskell. Over the last several years C# has extended it's general purpose features by introducing more and more functional language features: LINQ (list comprehension), Lamdas, Closures, Anonymous Delegates and more... Given C#'s adoption of these functional features and F#'s taxonomy as an impure functional language (it allows YOU to access framework libraries or change shared state when a function is called if you want to) there is a strong similarity between the two languages although each has it's own polar opposite primary emphasis. I'm interested in any successful models employing these two languages in your production polyglot programs and also the areas within production software (web apps, client apps, server apps) you have written in F# in the past year or so that you would previously have written in C#. EDIT: Edited based on feedback from close votes with the intent of reducing perceived ambiguity.

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• Why darcs instead of git?

  - by Ctrl Alt D-1337

  Using pure functional languages can have a lot of benefits over using impure imperatives but low level systems languages will generally allow you to achieve much greater performance especially when they are imperative because it allows you to specify the exact steps in how the cpu should compute the result. If there is ever list of tools where high performance is an absolute must then I would put source version controls systems right at the top of that list and git achieves this very well but performance is not it's only advantage over many other other types of version control systems anyway. The git team are handling the unsafe c code very well and I never worry about my type system or any other features of the language it is written in so why is it that there is a lot of haskell developers that must use darcs when they will only be using the finished product?

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• What's the best way to do literate programming in Python on Windows?

  - by JasonFruit

  I've been playing with various ways of doing literate programming in Python. I like noweb, but I have two main problems with it: first, it is hard to build on Windows, where I spend about half my development time; and second, it requires me to indent each chunk of code as it will be in the final program --- which I don't necessarily know when I write it. I don't want to use Leo, because I'm very attached to Emacs. Is there a good literate programming tool that: Runs on Windows Allows me to set the indentation of the chunks when they're used, not when they're written Still lets me work in Emacs Thanks! Correction: noweb does allow me to indent later --- I misread the paper I found on it. By default, notangle preserves whitespace and maintains indentation when expanding chunks. It can therefore be used with languages like Miranda and Haskell, in which indentation is significant That leaves me with only the "Runs on Windows" problem.

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• Common programming mistakes for Scala developers to avoid

  - by jelovirt

  In the spirit of Common programming mistakes for Java developers to avoid? Common programming mistakes for JavaScript developers to avoid? Common programming mistakes for .NET developers to avoid? Common programming mistakes for Haskell developers to avoid? Common programming mistakes for Python developers to avoid? Common Programming Mistakes for Ruby Developers to Avoid Common programming mistakes for PHP developers to avoid? what are some common mistakes made by Scala developers, and how can we avoid them? Also, as the biggest group of new Scala developers come from Java, what specific pitfalls they have to be aware of? For example, one often cited problem Java programmers moving to Scala make is use a procedural approach when a functional one would be more suitable in Scala. What other mistakes e.g. in API design newcomers should try to avoid.

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• Programming challenge: can you code a hello world program as a Palindrome?

  - by Assaf Lavie

  So the puzzle is to write a hello world program in your language of choice, where the program's source file as a string has to be a palindrome. To be clear, the output has to be exactly "Hello, World". Edit: Well, with comments it seems trivial (not that I thought of it myself of course [sigh].. hat tip to cobbal). So new rule: no comments. Edit: I feel kind of bad editing someone else's question to say this, but it will eliminate a lot of non-palindromes that keep popping up, and I'm tired of seeing the same simple mistake over and over. The following is NOT a palindrome: ()() The following IS a palindrome: ())( Brackets, parenthesis, and anything else that must match are a major barrier to palindrome-ing, yes, but that doesn't mean you can ignore them and post non-palindrome answers. Languages represented thus far: C, C++, Bash, elisp, C#, Perl, sh, Windows shell, Java, Common Lisp, Awk, Ruby, Brainfuck, Funge, Python, Machine Language, HQ9+, Assembly, TCL, J, php, Haskell, io, TeX, APL, Javascript, mIRC Script, Basic, Orc, Fortran, Unlambda, Pseudo-code, Befunge, CFML, Lua, INTERCAL, VBScript, HTML, sed, PostScript, GolfScript, REBOL, SQL

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• Very simple, terse and easy GUI programming “frameworks”

  - by jetxee

  Please list GUI programming libraries, toolkits, frameworks which allow to write GUI apps quickly. I mean in such a way, that GUI is described entirely in a human-readable (and human-writable) plain text file (code) code is terse (1 or 2 lines of code per widget/event pair), suitable for scripting structure and operation of the GUI is evident from the code (nesting of widgets and flow of events) details about how to build the GUI are hidden (things like mainloop, attaching event listeners, etc.) auto-layouts are supported (vboxes, hboxes, etc.) As answers suggest, this may be defined as declarative GUI programming, but it is not necessarily such. Any approach is OK if it works, is easy to use and terse. There are some GUI libraries/toolkits like this. They are listed below. Please extend the list if you see a qualifying toolkit missing. Indicate if the project is crossplatform, mature, active, and give an example if possible. Please use this wiki to discuss only Open Source projects. This is the list so far (in alphabetical order): Fudgets Fudgets is a Haskell library. Platform: Unix. Status: Experimental, but still maintained. An example: import Fudgets main = fudlogue (shellF "Hello" (labelF "Hello, world!" >+< quitButtonF)) GNUstep Renaissance Renaissance allows to describe GUI in simple XML. Platforms: OSX/GNUstep. Status: part of GNUstep. An example below: <window title="Example"> <vbox> <label font="big"> Click the button below to quit the application </label> <button title="Quit" action="terminate:"/> </vbox> </window> HTML HTML-based GUI (HTML + JS). Crossplatform, mature. Can be used entirely on the client side. Looking for a nice “helloworld” example. JavaFX JavaFX is usable for standalone (desktop) apps as well as for web applications. Not completely crossplatform, not yet completely open source. Status: 1.0 release. An example: Frame { content: Button { text: "Press Me" action: operation() { System.out.println("You pressed me"); } } visible: true } Screenshot is needed. Phooey Phooey is another Haskell library. Crossplatform (wxWidgets), HTML+JS backend planned. Mature and active. An example (a little more than a helloworld): ui1 :: UI () ui1 = title "Shopping List" $ do a <- title "apples" $ islider (0,10) 3 b <- title "bananas" $ islider (0,10) 7 title "total" $ showDisplay (liftA2 (+) a b) PythonCard PythonCard describes GUI in a Python dictionary. Crossplatform (wxWidgets). Some apps use it, but the project seems stalled. There is an active fork. I skip PythonCard example because it is too verbose for the contest. Shoes Shoes for Ruby. Platforms: Win/OSX/GTK+. Status: Young but active. A minimal app looks like this: Shoes.app { @push = button "Push me" @note = para "Nothing pushed so far" @push.click { @note.replace "Aha! Click!" } } Tcl/Tk Tcl/Tk. Crossplatform (its own widget set). Mature (probably even dated) and active. An example: #!/usr/bin/env wish button .hello -text "Hello, World!" -command { exit } pack .hello tkwait window . tekUI tekUI for Lua (and C). Platforms: X11, DirectFB. Status: Alpha (usable, but API still evolves). An example: #/usr/bin/env lua ui = require "tek.ui" ui.Application:new { Children = { ui.Window:new { Title = "Hello", Children = { ui.Text:new { Text = "_Hello, World!", Style = "button", Mode = "button", }, }, }, }, }:run() Treethon Treethon for Python. It describes GUI in a YAML file (Python in a YAML tree). Platform: GTK+. Status: work in proress. A simple app looks like this: _import: gtk view: gtk.Window() add: - view: gtk.Button('Hello World') on clicked: print view.get_label() Yet unnamed Python library by Richard Jones: This one is not released yet. The idea is to use Python context managers (with keyword) to structure GUI code. See Richard Jones' blog for details. with gui.vertical: text = gui.label('hello!') items = gui.selection(['one', 'two', 'three']) with gui.button('click me!'): def on_click(): text.value = items.value text.foreground = red XUL XUL + Javascript may be used to create stand-alone desktop apps with XULRunner as well as Mozilla extensions. Mature, open source, crossplatform. <?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <window id="main" title="My App" width="300" height="300" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <caption label="Hello World"/> </window> Thank your for contributions!

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• Clojure: Testing every value from map operation for truth

  - by Ralph

  How can I test that every value in the collection returned by map is true? I am using the following: (defn test [f coll] (every? #(identity %) (map f coll))) with the anonymous function #(identity %), but I was wondering if there is a better way. I cannot use (apply and ...) because and is a macro. UPDATE: BTW, I am making my way through The Haskell Road to Logic, Maths, and Programming, by Kees Doets and Jan can Eijck, but doing the exercises in Clojure. It's a very interesting book.

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• Does MATLAB perform tail call optimization?

  - by Shea Levy

  I've recently learned Haskell, and am trying to carry the pure functional style over to my other code when possible. An important aspect of this is treating all variables as immutable, i.e. constants. In order to do so, many computations that would be implemented using loops in an imperative style have to be performed using recursion, which typically incurs a memory penalty due to the allocation a new stack frame for each function call. In the special case of a tail call (where the return value of a called function is immediately returned to the callee's caller), however, this penalty can be bypassed by a process called tail call optimization (in one method, this can be done by essentially replacing a call with a jmp after setting up the stack properly). Does MATLAB perform TCO by default, or is there a way to tell it to?

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• Learning Algorithms and Data Structures Fundamentals

  - by valya

  Can you recommend me a book or (better!) a site with many hard problems and exercises about data structures? I'm already answering project Euler questions, but these questions are about interesting, but uncommon algorithms. I hardly used even a simple tree. Maybe there is a site with exercises like: hey, you need to calculate this: ... . Do it using a tree. Now do it using a zipper. Upload your C (Haskell, Lisp, even Pascal or Fortress go) solution. Oh, your solution is so slow! Self-education is very hard then you trying to learn very common, fundamental things. How can I help myself with them without attending to courses or whatever?

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• What are the common programming mistakes in Python?

  - by Paul McGuire

  I was about to tag the recent question in which the OP accidentally shadowed the builtin operator module with his own local operator.py with the "common-mistakes" tag, and I saw that there are a number of interesting questions posted asking for common mistakes to avoid in Java, Ruby, Scala, Clojure, .Net, jQuery, Haskell, SQL, ColdFusion, and so on, but I didn't see any for Python. For the benefit of Python beginners, can we enumerate the common mistakes that we have all committed at one time or another, in the hopes of maybe steering a newbie or two clear of them? (In homage to "The Princess Bride", I call these the Classic Blunders.) If possible, a little supporting explanation on what the problem is, and the generally accepted resolution/workaround, so that the beginning Pythoner doesn't read your answer and say "ok, that's a mistake, how do I fix it?"

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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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• Vim or Emacs for software development

  - by Justin

  I'm not trying to start any wars here, just get some good info. I'm getting a little exhausted using numerous IDE's for development (VS, XCode, Eclipse/Netbeans, and TextMate) and am looking for a replacement I can use on all the different machines I interact with. What are some of the pros of Vim/Emacs for things like Languages supported Syntax highlighting (for things such as c, objc-c, c#, java, python, haskell, html, javascript, xml etc...) Code completion Code folding Working with a directory of files (like have a solution/project opened) Possible debugger support What are some of the main things you like about (Emacs/Vim, and please no flames only what you really like) Thanks =) *(yes.. I have scoured the net reading this vs that etc. but I'd like more of a 'why you love it' vs 'this is better than that because...')

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• Suggest resources for learning Scheme.

  - by EmFi

  I'll be starting a new job soon where Scheme is heavily used. I currently do not know Scheme, but my employer assures me that is not a problem. Regardless I'd like to hit the ground running and have a working knowledge of the language before my start date. So I'm looking for good resources from which to learn Scheme. I have had minimal exposure to functional languages. Really only a small chunk of a course devoted to Haskell. But I have a strong background in procedural and OO and procedural languages. Before it gets requested by a commenter, I am competent with the following languages: C, C++, C#, Java, Perl, Python, and Ruby.

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• What production software have you written in F# in the past year or so that you would previously hav

  - by Peter McGrattan

  Over the last few years F# has evolved into one of Microsoft's fully supported languages employing many ideas incubated in OCaml, ML and Haskell. Over the last several years C# has extended it's general purpose features by introducing more and more functional language features: LINQ (list comprehension), Lamdas, Closures, Anonymous Delegates and more... Given C#'s adoption of these functional features and F#'s taxonomy as an impure functional language (it allows YOU to access framework libraries or change shared state when a function is called if you want to) there is a strong similarity between the two languages although each has it's own polar opposite primary emphasis. I'm interested in any successful models employing these two languages in your production polyglot programs and also the areas within production software (web apps, client apps, server apps) you have written in F# in the past year or so that you would previously have written in C#.

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• Is there an equivalent for the Zip function in Clojure Core or Contrib?

  - by John Kane

  In Clojure, I want to combine two lists to give a list of pairs, > (zip '(1 2 3) '(4 5 6)) ((1 4) (2 5) (3 6)) In Haskell or Ruby the function is called zip. Implementing it is not difficult, but I wanted to make sure I wasn't missing a function in Core or Contrib. There is a zip namespace in Core, but it is described as providing access to the Zipper functional technique, which does not appear to be what I am after. Is there an equivalent function for combining 2 or more lists, in this way, in Core? If there is not, is it because there is an idiomatic approach that renders the function unneeded?

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• Function Composition in C++

  - by Channel72

  There are a lot of impressive Boost libraries such as Boost.Lambda or Boost.Phoenix which go a long way towards making C++ into a truly functional language. But is there a straightforward way to create a composite function from any 2 or more arbitrary functions or functors? If I have: int f(int x) and int g(int x), I want to do something like f . g which would statically generate a new function object equivalent to f(g(x)). This seems to be possible through various techniques, such as those discussed here. Certainly, you can chain calls to boost::lambda::bind to create a composite functor. But is there anything in Boost which easily allows you to take any 2 or more functions or function objects and combine them to create a single composite functor, similar to how you would do it in a language like Haskell?

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• In what specific areas has F# proven more applicable than C#?

  - by Peter McGrattan

  Over the last few years F# has evolved into one of Microsoft's fully supported languages employing many ideas incubated in OCaml, ML and Haskell. Over the last several years C# has extended it's general purpose features by introducing more and more functional language features: LINQ (list comprehension), Lamdas, Closures, Anonymous Delegates and more... Given C#'s adoption of these functional features and F#'s taxonomy as an impure functional language (it allows YOU to access framework libraries or change shared state when a function is called if you want to) there is a strong similarity between the two languages although each has it's own polar opposite primary emphasis. I'm interested in any successful models employing these two languages in your production polyglot programs and also the areas within production software (web apps, client apps, server apps) you have written in F# in the past year or so that you would previously have written in C#. EDIT: Altered title with the intent of reducing perceived ambiguity.

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• How can I maximally partition a set?

  - by Gregory Higley

  I'm trying to solve one of the Project Euler problems. As a consequence, I need an algorithm that will help me find all possible partitions of a set, in any order. For instance, given the set 2 3 3 5: 2 | 3 3 5 2 | 3 | 3 5 2 | 3 3 | 5 2 | 3 | 3 | 5 2 5 | 3 3 and so on. Pretty much every possible combination of the members of the set. I've searched the net of course, but haven't found much that's directly useful to me, since I speak programmer-ese not advanced-math-ese. Can anyone help me out with this? I can read pretty much any programming language, from BASIC to Haskell, so post in whatever language you wish.

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• routine to generate a 2d array from two 1d arrays and a function

  - by intuited

  I'm guessing that there's a word for this concept, and that it's available in at least some popular languages, but my perfunctory search was fruitless. A pseudocode example of what I'd like to do: function foo(a, b) { return a * b // EG } a = [ 1, 2, 3 ] b = [ 4, 5, 6 ] matrix = the_function_for_which_I_search(foo, [a, b] ) print matrix => [ [ 4, 8, 12], [5, 10, 15], [6, 12, 18] ] // or function concatenate(a,b) return a.b } print the_function_for_which_I_search( concatenate, [ a, b ]) => [ [ '14', '24', '34'], ['15', '25', '35'], [16', '26', '36'] ] In other words, function_for_which_I_search will apply the function given as its first argument to each combination of the elements of the two arrays passed as its second argument, and return the results as a two-dimensional array. I would like to know if such a routine has a common name, and if it's available in a python module, cpan package, ruby gem, pear package, etc. I'm also wondering if this is a core function in other languages, maybe haskell or R?

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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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• Is there a good reason Uni courses still use "academic" languages like modula2?

  - by Cheeso

  This question prompts me to ask - why do universities still teach in languages like Modula2, when improved modern languages are available for free? Are there uni's that still teach Pascal, for example? I mean, it was good 30 years ago, but... now? Why? Why not Java, C#, Haskell? Related: Is it backwards to still teach LISP? Is this a duplicate question? If not, I think it ought to be a community wiki topic.

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• freeGLUT keyboard input

  - by peaker

  I'm using GLUT (freeglut3) (via the Haskell GLUT bindings). import Graphics.UI.GLUT handleKBMouse :: KeyboardMouseCallback handleKBMouse key keyState mods mousePos = do print (key, keyState, mods, mousePos) main :: IO () main = do getArgsAndInitialize createWindow "testTitle" keyboardMouseCallback $= Just handleKBMouse mainLoop It seems that various important keys (e.g: Shift+Tab) do not call my callback. Also, "mods" doesn't describe the win-key, only Ctrl, Shift and Alt. Having such limited access to keyboard input is a serious impediment for real application development. Am I doing anything wrong here or is just freeglut just crippled? Is GLUT crippled in general?

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• Which programming paradigm or language open most your mind?

  - by Dom De Felice

  It is often said that some programming languages exist that once grasped can open your mind and change the way you write software. A sort of "software design enlightenment", we can say. I heard this about Lisp, Smalltalk, Haskell, pure functional programming in general.. What are your experiences about this? I know that the right language to use depends on your needs, but I would like to know the one that better improve your programming skills in general. What do you think would be the best language/paradigm to learn to end up being a better programmer in the long run?

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