[Haskell-cafe] Code review: efficiency question

[Evan Martin]

I remember reading a tutorial that pointed out that you can often
avoid explicit recusion in Haskell and instead use higher-level
operators.

For your code, I think
  drawModals = foldr (flip (>>)) (return ()) . map drawModal
works(?).

On 5/2/06, Brian Hulley <brianh at metamilk.com> wrote:
> Hi -
> I started off writing the following piece of monadic code:
>
>     let
>           drawModal :: Control -> ManagerM ()
>           drawModal c = do -- details omitted
>
>           -- Prolog style coding...
>           drawModals :: [Control] -> ManagerM ()
>           drawModals [] = return ()
>           drawModals (c:cs) = do
>                                                drawModals cs
>                                                drawModal c
>     drawModals cs
>
> then it struck me that I should have not bothered with drawModals and
> instead should just have used:
>
>     mapM_ drawModal (reverse cs)
>
> However, while this looks more elegant, it is less efficient?
> In other words, how much optimization can one assume when writing Haskell
> code?
> I'm trying to get a rough idea so I can decide whether to write helper
> functions such as drawModals in future or whether I should always just use
> the most elegant code instead.
>
> Any ideas?
>
> Thanks, Brian.
>
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