loops - Haskell - List Error -

i'm trying iterate list , square number , add them together

sumsq  (x:xs) =  let total = 0 loop length(x:xs) (x:xs) total   loop 0 (x:xs) = return () loop n (x:xs)  total =      let          sq = ((x:xs)!!n)^2         total = total + sq     loop ((n-1) (x:xs) total) 

but i'm getting parse error in loop. going wrong?

also there better way this?

first of - miss spaces! significant.

second, forget in let ... in. not use in in do-notation:

sumsq  (x:xs) =     let total = 0 in    loop length(x:xs) (x:xs) total 

third, not use x , xs form (x:xs) :

sumsq  xs =      let total = 0 in     loop (length xs) xs total 

and unite our length xsin 1 block. fourth.

fifth, have 3, not 2 arguments loop:

loop 0 xs total  = return total 

sixth, (!!) work 0, use 1, (xs !! (n -1)) right

seventh, don't need use monad, recursion. so, rid return , do

eighth. have infinite recursive total = total + smth

ninth, can't use arguments tuple, so, final working result :

sumsq  xs =      let total = 0 in     loop (length xs) xs total   loop 0 xs total = total loop n xs total = loop (n-1) xs total1              sq = (xs !! (n -1)) ^2         total1 = total + sq 

updated

if talking complexity, not - o(n^2) mentioned in comments : each element seek element. simplify our loop function , rid of n argument:

loop []     total = total loop (x:xs) total = loop xs total1              sq = x ^ 2         total1 = total + sq 

and our sumsq function write:

sumsq  xs = loop xs 0 

p.s. implementation easier function sumsq = sum. map (^ 2)