[Haskell-cafe] List operation question

[ihope]

On 2/4/07, Eric Olander <olandere at gmail.com> wrote:
> Hi,
>    I'm still somewhat new to Haskell, so I'm wondering if there are better
> ways I could implement the following functions, especially shiftl:
>
> >> moves the last element to the head of the list
>     shiftl :: [a] -> [a]
>     shiftl [] = []
>     shiftl x = [last x] ++ init x

Well, you could try this, though I'm actually sure it's any faster:

> shiftl (x1:x2:xs) = last:x1:init
>                       where last:init = shiftl (x2:xs)
> shiftl [x] = [x]
> shiftl [] = error "shiftl: empty list"

Or, if you don't want to give an error on [], omit the last line and
replace both of the [x] with xs.