Here is a parallel map in Haskell pmap f xs = map f xs `using` parList rdeepseq The cool thing about this is that `map` is just the regular map function.

Here is a parallel map in Haskell pmap f xs = map f xs `using` parList rdeepseq The cool thing about this is that `map` is just the regular map function. However, as Haskell is lazy, `map f xs` returns a thunk and is not immediately evaluated. `using` allows you to evaluate the resultant thunk using any "evaluation strategy", and `parList rdeepseq` describes a strategy for evaluating lists in parallel! Also, like the Erlang VM, GHC has fast, lightweight "green threads". Edit: Another way to write it would be pmap _ [] = [] pmap f (x:xs) = runEval $ do x' <- rpar (f x) xs' <- rpar (pmap f xs) return $ (x':xs')