Re: [Haskell] Types of when and unless in Control.Monad

On 22 April 2012 21:39, Christian Höner zu Siederdissen wrote:

* Julian Gilbey [22.04.2012 09:22]:

...

On Sat, Apr 21, 2012 at 08:28:27PM -0500, Strake wrote:

...

On 21/04/2012, Andreas Abel wrote:

...

to avoid silly "return ()" statements like in

   when cond $ do      monadicComputationWhoseResultIWantToDiscard      return ()

(when cond ∘ void) monadicComputationWhoseResultIWantToDiscard or when cond $ () <$ monadicComputationWhoseResultIWantToDiscard

How is that simpler than

  when cond monadicComputationWhoseResultIWantToDiscard

which it would be with the suggested new type?

   Julian

Wouldn't "when_" and "unless_" or similar be better? I'd probably like to have the compiler annoy me, since it is not clear that I want to discard the result. If I really want to discard, I should have to make it clear as there is probably a good reason for the inner function to return a result in the first place?

Agreed; I'm not sure if I agree with having such functionality (Henning makes some good points), but if people deem it desirable then I think it would be better to have them with new names for the reasons you state. -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com http://IvanMiljenovic.wordpress.com