字符串列表中的 Haskell 数组

Question

So I have a list of strings and the task is to count how many times each string can be met in that list. I used maps:

freqMap =  M.fromListWith (+) [(c, 1) | c <- subs]

and just sorting:

frequency list = map (\l -> (length l, head l)) $ group (sort list)

but it's all too slow for my task - the original list is very large. I've heard, that using unboxed arrays can be very fast. Like for list of integers:

histogram bounds xs = accumArray (+) 0 bounds [(x, 1) | x <- xs]

As String is not a member of Ix class, the question is: is it possible to build an array from list of strings?

Answer 1

Data.HashMap (lazy/strict) is a faster version of the vanilla haskell maps - using them may speed up your operations if the bottleneck is primarily the update/lookup speed.

And the best part is that you can keep the nice clean approach you've already written, and not have to write (usually uglier) code that interacts with arrays.