product of list iteratively

Question

I\'m trying to learn coding in Haskell.

I started with an easy example \"the product of a list\".

product :: [Integer] -> Integer  
product []     = 1         


        

Answer 1

Well in Haskell we don't have loops so iterative is relative, but here's the "functional iteration approach"

 product = foldl' (*) 1

folds are the equivalent of loops in imperative languages. foldl' in particular is tail recursive and strict so it will run in constant space, similar to a loop.

If we were to write it explicitly

 product = go 1
   where go accum (x:xs) = go (accum * x) xs
         go accum _      = accum -- Subtle performances
                                 -- differences with strictness

This is still recursive, but will compile to similar assembly.