Using Haskell's map function to calculate the sum of a list

Question

Haskell

addm::[Int]->Int
addm (x:xs) = sum(x:xs)

I was able to achieve to get a sum of a list using sum fu

Answer 1

I realize this question has been answered, but I wanted to add this thought...

listLen2 :: [a] -> Int
listLen2 = sum . map (const 1)

I believe it returns the constant 1 for each item in the list, and returns the sum! Might not be the best coding practice, but it was an example my professor gave to us students that seems to relate to this question well.