Top "Haskell" questions

Haskell is a functional programming language featuring strong static typing, lazy evaluation, extensive parallelism and concurrency support, and unique abstraction capabilities.

Does Haskell have variables?

I've frequently heard claims that Haskell doesn't have variables; in particular, this answer claims that it doesn't, and it was …

variables haskell immutability monads referential-transparency
Implications of foldr vs. foldl (or foldl')

Firstly, Real World Haskell, which I am reading, says to never use foldl and instead use foldl'. So I trust …

recursion functional-programming fold haskell
Deploying Yesod to Heroku, can't build statically

I'm very new to Yesod and I'm having trouble building Yesod statically so I can deploy to Heroku. I have …

linux haskell heroku static-linking yesod
In Haskell, how do you trim whitespace from the beginning and end of a string?

How do you trim whitespace from the start and end of a string? trim " abc " => "abc" Edit: Ok, let …

string haskell trim removing-whitespace
Haskell or Standard ML for beginners?

I'm going to be teaching a lower-division course in discrete structures. I have selected the text book Discrete Structures, Logic, …

haskell functional-programming sml discrete-mathematics
How would you define map and filter using foldr in Haskell?

I'm doing a bit of self study on functional languages (currently using Haskell). I came across a Haskell based assignment …

haskell map functional-programming filter fold
Why is there "data" and "newtype" in Haskell?

It seems that a newtype definition is just a data definition that obeys some restrictions (e.g., only one constructor), …

haskell types language-design type-systems
Why does this Haskell code produce the "infinite type" error?

I am new to Haskell and facing a "cannot construct infinite type" error that I cannot make sense of. In …

haskell types type-inference
What does $ mean/do in Haskell?

When you are writing slightly more complex functions I notice that $ is used a lot but I don't have a …

haskell syntax operators dollar-sign
Multi-line commands in GHCi

I am having problem in entering multi-line commands in ghci. The following 2-line code works from a file: addTwo :: Int …

haskell ghci