I would like to to choose one of these languages for building web applications. I'm not interested in framework per se, but have the following needs: Rapid development. Easy to scale. Strong community for the web. Quick and easy to deploy. I'm very familiar with Haskell, and have some familiarity with scheme (in particular PLT). Sch...
Hello, I would like to know what is the best solution to create simple menu with functionality described below (pseudo code) just like im used to: while (true){ x = readLine(); case (x): x == "1" then do sth1 function x == "2" then do sth2 function } thanks for help, maybe any other ideas on how to make menu ...
I want to create a function apply that takes a function with an arbitrary amount of arguments as well as a list of integers, and returns the result of the function (Where each integer in the list is an argument in order. I was thinking something like: apply :: ([Int] -> Int) -> [Int] -> Int apply f x:xs = apply (f x) xs apply f [] = f ...
I'm writing a program to solve the result of primitive recursive functions: 1 --Basic functions------------------------------ 2 3 --Zero function 4 z :: Int -> Int 5 z = \_ -> 0 6 7 --Successor function 8 s :: Int -> Int 9 s = \x -> (x + 1) 10 11 --Identity/Projection function generator 12 idnm :: Int -> Int -> ([In...
21 --Primitive recursion constructor 22 pr :: ([Int] -> Int) -> ([Int] -> Int) -> ([Int] -> Int) 23 pr f g = \xs 0 -> f xs 24 pr f g = \xs (y+1) -> g xs y ((pr f g) xs y) I want the function this function creates to act differently on different inputs, so that it can create a recursive function. As expected, the above code doesn't ...
I've recently started to learn Haskell. I have this code module Main where import IO main = do hSetBuffering stdin LineBuffering putStrLn "Please enter your name: " name <- getLine putStrLn ("Hello, " ++ name ++ ", how are you?") I'm using the GHC compiler together with the notep...
Hi everbody I need to change my F# code to Haskell code but I am so new in Haskell and I can not this My code simply read data from keyboard if data not an integer return an error message then calculate the n fibonacci number then writes to a list after that writes the list into a txt file Here is my code open System let rec fib n = ...
When profiling a Haskell program written in GHC, the names of typeclass functions are mangled in the .prof file to distinguish one instance's implementations of them from another. How can I demangle these names to find out which type's instance it is? For example, suppose I have the following program, where types Fast and Slow both imp...
Most of the problems I have to solve in my job as a developer have to do with data modeling. For example in a OOP Web Application world I often have to change the data properties that are in a object to meet new requirements. If I'm lucky I don't even need to programmatically add new "behavior" code (functions,methods). Instead I can de...
I need a simple function is_square :: Int -> Bool which determines if an Int N a perfect square (is there an integer x such that x*x = N). Of course I can just write something like is_square n = sq * sq == n where sq = floor $ sqrt $ (fromIntegral n::Double) but it looks terrible! Maybe there is a common simple way to implemen...
I'm kind of new in Haskell and I have difficulty understanding how inferred types and such works. map :: (a -> b) -> [a] -> [b] (.) :: (a -> b) -> (c -> a) -> c -> b What EXACTLY does that mean? foldr :: (a -> b -> b) -> b -> [a] -> b foldl :: (a -> b -> a) -> a -> [b] -> a foldl1 :: (a -> a -> a) -> [a] -> a What are the differenc...
foldr:: (a -> b -> b) -> b -> [a] -> b map :: (a -> b) -> [a] -> [b] mys :: a -> a (.) :: (a -> b) -> (c -> a) -> c -> b what is inferred type of: a.map mys :: b.mys map :: c.foldr map :: d.foldr map.mys :: I've tried to create mys myself using mys n = n + 2 but the type of that is mys :: Num a => a -> a What's the difference bet...
Hello, Could someone explain me what this code does line by line ? how t ounderstand excactly first line with declaration ? what does it mean: [Prop (Grid ())]? thanks for help gridCtrl :: Window a -> [Prop (Grid ())] -> IO (Grid ()) gridCtrl parent props = feed2 props 0 $ initialWindow $ \id rect -> \props flags -> do g <- ...
I don't understand the exact algebra and theory behind Haskell's monads. However, when I think about functional programming in general I get the impression that state would be modelled by taking an initial state and generating a copy of it to represent the next state. This is like when one list is appended to another; neither list gets...
First of all, it's great. However, I came across a situation where my benchmarks turned up weird results. I am new to Haskell, and this is first time I've gotten my hands dirty with mutable arrays and Monads. The code below is based on this example. I wrote a generic monadic for function that takes numbers and a step function rather...
Hello! (This question is related to my previous question, or rather to my answer to it.) I want to store all qubes of natural numbers in a structure and look up specific integers to see if they are perfect cubes. For example, cubes = map (\x -> x*x*x) [1..] is_cube n = n == (head $ dropWhile (<n) cubes) It is much faster than calcu...
Recently when I have found good sources packages for ghc 6.12/6.10 on Hackage I've been forced to do some minor or major changes to the cabal files to make those packages to work under windows. Besides to fork and merge my fixes with github, what seems to be the best way/ good enough practice to take these modified builds to a couple of ...
Hello, Im using tutorials from wxHaskell and want to display content of table movies in the grid. HEre is my code : {-------------------------------------------------------------------------------- Test Grid. --------------------------------------------------------------------------------} module Main where import Graphics.UI.WX i...
I use Ctrl p a lot instead of up arrow to go up on Terminal. How to make ghci support Ctrl p to go up? I use ghci from ghc98 from port. Mac OS X 10.5.8. ...
I was working on a Rails template and was trying to write a bit of code that allows me to populate a table or multiple columns of ul tags "top-to-bottom" and "left-to-right" across however many columns I specify. I'm just getting the hang of Ruby so I couldn't figure this out. I'm also curious about an idiomatic Haskell version for this ...