Haskell is an advanced purely-functional programming language. An open-source product of more than twenty years of cutting-edge research, it allows rapid development of robust, concise, correct software. With strong support for integration with other languages, built-in concurrency and parallelism, ...
1
vote
1answer
17 views
happy: reduce/reduce conflict
Why this raises a warning about reduce/reduce conflict
root : set1 'X'
| set2 'X' 'X'
set1 : 'A'
| 'B'
set2 : 'B'
| 'C'
but the next is ok?
...
1
vote
1answer
34 views
Implementing >>= in newtype
Let me start from the task I want solve, probably I'm going wrong way. I use Snap framework for toy project, and the main is that it's functions under Snap monad. I need to add my state above it. I ...
0
votes
0answers
42 views
Write to file without \" symbols haskell
For example need this text to write a file:
This is some simple text "it's quote", test test
I use writeFile :: FilePath -> String -> IO () to write file, but when i try to write this string ...
8
votes
2answers
119 views
Evolving data structure
I'm trying to write a compiler for a C-like language in Haskell. The compiler progresses by transforming an AST. The first pass parses the input to create the AST, tying a knot with the symbol table ...
1
vote
1answer
62 views
Matrix operation in Haskell
I have a problem to unfold a matrix. Here is how the output of the programm should look like. I am little bit stuck.
unfoldMatrix :: [ [a] ] -> [a]
Main> unfoldMatrix [[1, 2, 3],
...
0
votes
1answer
67 views
Quick Check for CoffeeScript
Does it exist? I can't find it and it isn't listed on wikipedia. (which means it doesn't exist :) )
I know node.js has it. Not sure if writing my node app in coffeescript and applying quick check ...
1
vote
1answer
38 views
Using monadic validation with Digestive Functors and Snap
I try quite a while now to wrap my head around how to use validation in a digestive functors form field, that requires access to another monad. To cut it short I have a digestive form like this
...
0
votes
1answer
28 views
Install part of program with cabal like library
I have simple program written with haskell, i build it with cabal. For example i my program has next directory structure:
my-prog
* Main.hs
* my-prog.cabal
* SomeDirWithHsFiles
- File1.hs
...
0
votes
3answers
117 views
How to concat two (IO) Strings in Haskell?
I know this sound very simple, but I failed to combine two strings into a new one.
The IO String "a" from a gtk entry is fetched by
a <- (entryGetText text_field)
The goal is to combine ...
0
votes
2answers
97 views
Undefined and Developing (Part 2)
I've already asked the question about undefined. And because it is impossible to do such thing, I will describe the case when this can be useful. But I think the question is common and can be useful ...
26
votes
3answers
315 views
What's the theoretical basis for existential types?
The Haskell Wiki does a good job of explaining how to use existential types, but I don't quite grok the theory behind them.
Consider this example of an existential type:
data S = forall a. Show a ...
1
vote
1answer
34 views
XMonad: SpawnOn workspace that had focus when spawn key was pressed
I would like to have my programs spawn on the screen that was in focus when its keybinding was pressed not on the screen thats currently in focus when it finishes loading.
Why:
My current setup is ...
2
votes
2answers
80 views
Render any Literate Haskell to PDF, HTML, or similar
How to I convert a Literate Haskell file to something easier on the eyes? Here's what happens when I try to do the obvious thing:
$ latex Check.lhs
This is pdfTeX, Version 3.1415926-1.40.10 (TeX ...
4
votes
5answers
103 views
Creating a new Ord instance for Lists
This is my first attempt at creating a custom instance of a class such as Ord.
I've defined a new data structure to represent a list:
data List a = Empty | Cons a (List a)
deriving (Show, Eq)
...
0
votes
2answers
59 views
Parsec lookahead to handle ints
I'm working on a Parsec parser to handle a somewhat complex data file format (and I have no control over this format).
I've made a lot of progress, but am currently stuck with the following.
I need ...
