Using an accumulator, "iterating"...
Sat, 21 Jun 2003 02:46:09 +0100
Brett Kelly wrote:
> I'm trying to write a function that takes a list and a element (same type) and
> returns the index of the first instance of the element in the list. like:
> getindex "brett" 'e' would return 2, etc.
> i'm trying to accomplish this using an accumulator, here's what i've got:
> pyindex :: Eq a => a -> [a] -> Maybe Int
> pyindex c l = pyindex' 0 chr (x:xs)
None of chr, x or xs are defined here; if you change the above line
pyindex c l = pyindex' 0 c l
Except that you will get a match failure if the list doesn't contain
the specified element, so you also need a base case:
pyindex' _ _  = Nothing
Glynn Clements <firstname.lastname@example.org>