Finding index of element in a list in Haskell?

import Data.List
elemIndex 'b' "abc" === Just 1

A really good tool for finding haskell functions is Hoogle. Allows you to search by type signature among other things.

If you wanted to do everything in one pass I'd recommend Data.List.mapAccumL, passing the index of the largest number found so far along as the accumulator.

How to find the index of the maximum element? How about trying all indexes and checking whether they are the maximum?

ghci> let maxIndex xs = head $ filter ((== maximum xs) . (xs !!)) [0..]

But this sounds like something for which a function already exists. My code will be more readable, maintainable, and probably even more efficient, if I used the existing function.

FYI, you can also ask Hoogle that can search by Haskell type signatures (as Will suggested):

$ hoogle "Ord a => [a] -> Int" | head

<Nothing relevant>

$ # hmm, so no function to give me the index of maximum outright,
$ # but how about finding a specific element, and I give it the maximum?
$ hoogle "a -> [a] -> Int" | head
Data.List elemIndex :: Eq a => a -> [a] -> Maybe Int
Data.List elemIndices :: Eq a => a -> [a] -> [Int]