[Haskell-beginners] Beginners Digest, Vol 41, Issue 30

[Daniel Fischer]

On Wednesday 23 November 2011, 00:21:33, Lee Short wrote:
>  That's not my actual code, I was just using it as a simplified example

Glad to read that.

>  and didn't put a lot of thought into it.  My actual code is
> 
>  if delete /= ""
>     then if exists
>           then deleteFromTable req t key
>           else return ()
>     else if exists
>           then updateTable req t key
>           else insertTable req t
> 
>  I'd love to hear comments on how to make that more idiomatic, if 
>  there's a way.

Hmm, harder, much harder.

You can replace the

    if exists
      then deleteFromTable req t key
      else return ()

with

    when exists (deleteFromTable req t key)

and instead of comparing to "", you can use null, so

if null delete
  then if exists
         then updateTable req t key
         else insertTable req t
  else when exists (deleteFromTable req t key)

I would recommend the when. Concerning the null vs. /= "", I prefer null, 
but I'm not religious about it.