Function to find the index of an element in a list

Question

Is there a function in Haskell that takes as arguments a list and an element in that list and returns the index of that element in the list, i.e.

If I had the list ['a','f','d','g','b','h'] and the element 'b' it would return 4?

bheklilr · Accepted Answer · 2013-10-09 19:44:15Z

3

You're looking for the elemIndex function in Data.List:

> :m +Data.List
> :t elemIndex
elemIndex :: Eq a => a -> [a] -> Maybe Int
> elemIndex 'c' "abcde"
Just 2

answered Oct 9, 2013 at 19:44

bheklilr

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1 Comment

I think that worth teaching the fromJust function, too. :) More references at Data.Maybe.