Hello all,
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)
where pyindex' count chr (x:xs) = do
if x == chr then return count
else pyindex' (count + 1) chr xs
now, i know i've got a syntax problem, because i'm pretty sure my logic is correct (or at least MOSTLY correct).
can anybody see what's wrong with my stuff?
Sure. Three comments:
1) You don't need (or want) the `do' -- that's used for dealing with monads.
2) The function's signature indicates a return type of `Maybe Int', yet you're trying to return an Int.
3) What if you _don't_ find the target?
Additional comments:
The `if...then...else' form may not be the clearest way -- or the most `Haskell-ish' way of expressing this computation.
You may want to look through the standard prelude to find how things like this are usually done.
Good luck and HTH, --ag -- Artie Gold -- Austin, Texas
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