```
f x = (some expresion) x
```

you can simply write
```
f = some expression
```

We use this method to remove the `l`:
> -- Version 4
> evenSum :: Integral a => [a] -> a
>
> evenSum = accumSum 0
> where
> accumSum n [] = n
> accumSum n (x:xs) =
> if even x
> then accumSum (n+x) xs
> else accumSum n xs