I've been using Haskell for several months, and I love it—it's gradually become my tool of choice for everything from one-off file renaming scripts to larger XML processing programs. I'm definitely still a beginner, but I'm starting to feel comfortable with the language and the basics of the theory behind it. I'm a lowly graduate studen...
Hello, How can I make scrollable Grid in wxHaskell ? thanks ...
In the dependencies section of a cabal file: Build-Depends: base >= 3 && < 5, transformers >= 0.2.0 Should I be doing something like Build-Depends: base >= 3 && < 5, transformers >= 0.2.0 && < 0.3.0 (putting upper limits on versions of packages I depend on) or not? I'll use a real example: my "List" package on Hackage (List monad...
I have an assignment and am currently caught in one section of what I'm trying to do. Without going in to specific detail here is the basic layout: I'm given a data element, f, that holds four different types inside (each with their own purpose): data F = F Float Int, Int a function: func :: F -> F-> Q Which takes two data eleme...
The idea that the standard Monad class is flawed and that it should actually extend Functor or Pointed is floating around. I'm not necessarily claiming that it is the right thing to do, but suppose that one was trying to do it: import Prelude hiding (Monad(..)) class Functor m => Monad m where return :: a -> m a join :: m (m a...
Hello, I'm writing GUI app in haskell. I use sqlite to gather data and want to use grid in wxHASKELL TO present data in app. Everything is all right but I want to have possibility to add rows from haskell app. I achieved that but when I refresh it It expands and covers other controls. To make things short how can I set maximum size of...
I try to develop a simple average function in Haskell. This seems to work: lst = [1, 3] x = fromIntegral (sum lst) y = fromIntegral(length lst) z = x / y But why doesn't the following version work? lst = [1, 3] x = fromIntegral.sum lst y = fromIntegral.length lst z = x / y ...
I have homework where I am to update a list using a function that takes two elements and returns a value of part of the first element given in the function. So it's required to update the entire listing by going through each element and update its value by applying the function against all other elements in the list (including itself). ...
Say I have the following Haskell tree type, where "State" is a simple wrapper: data Tree a = Branch (State a) [Tree a] | Leaf (State a) deriving (Eq, Show) I also have a function "expand :: Tree a -> Tree a" which takes a leaf node, and expands it into a branch, or takes a branch and returns it unaltered. Th...
I'm a C++ Programmer trying to teach myself Haskell and it's proving to be challenging grasping the basics of using functions as a type of loop. I have a large number, 50!, and I need to add the sum of its digits. It's a relatively easy loop in C++ but I want to learn how to do it in Haskell. I've read some introductory guides and am a...
I have the following haskell code: fac n = product [1..n] taylor3s w0 f f' f'' t h = w1 : taylor3s w1 f f' f'' (t+h) h where hp i = h^i / fac i w1 = w0 + (hp 1) * f t w0 + (hp 2) * f' t w0 + (hp 3) * f'' t w0 taylor_results = take 4 $ taylor3s 1 f f' f'' 1 0.25 where f t x = t^4 - 4*x/t f' t x = 4*t^3 - 4*(f t x...
I'd like to rewrite such function into F#: zipWith' :: (a -> b -> c) -> (a -> c) -> (b -> c) -> [a] -> [b] -> [c] zipWith' _ _ h [] bs = h `map` bs zipWith' _ g _ as [] = g `map` as zipWith' f g h (a:as) (b:bs) = f a b:zipWith f g h as bs My first attempt was: let inline private map2' (xs : seq<'T>) (ys : seq<'U>) (f ...
I just downloaded the Haskell and J modes off of SourceForge, and I'm having trouble figuring out how to make them interface with emacs 23. Google searches yield detailed instructions for emacs 22, but it looks like changes have been made that make it hard to figure out where I'm supposed to stick the source files. The internal documenta...
I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing existentials. I got the existential data type data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm t...
Hi. I try process file which writen by russian symbols. When read and after write text to file i get something like: "\160\192\231\229\240\225\224\233\228\230\224\237" How i can get normal symbols ? Thanks ...
particularly indentation and under_score/camelCase/longalllowercasewords. ...
I have installed the latest Haskell Platform for MAC OSX and I get the error "Setup: failed to parse output of 'ghc-pkg dump'" when I do anything with Cabal. So I looked at my versions: ralphtq$ ghc-pkg list Cabal /Library/Frameworks/GHC.framework/Versions/612/usr/lib/ghc-6.12.1/package.conf.d Cabal-1.8.0.2 ralphtq-mac-mini:cabal-...
I'm nearly ready to upload my first package to Hackage! I have this in my hstest.cabal: Executable hstest Main-Is: hstest.hs Build-Depends: base, mtl, directory, ghc, ghc-paths, random, QuickCheck I understand that it's bad form to simply list which packages my package depends upon; instead I should state whic...
G'day guys, Trying currently to finish up a bit of homework I'm working on, and having an issue where I'm trying to apply map across a function that accepts multiple inputs. so in the case I'm using processList f (x:xs) = map accelerateList f xs x xs processList is given a floating value (f) and a List that it sorts into another List ...
One last question for the evening, I'm building the main input function of my Haskell program and I have to check for the args that are brought in so I use args <- getArgs case length args of 0 -> putStrLn "No Arguments, exiting" otherwise -> { other methods here} Is there an intelligent way of setting up other methods, or is...