[Haskell-cafe] proposal: point free case expressions

[Sebastiaan Visser]

On Nov 5, 2009, at 6:26 PM, Jonathan Daugherty wrote:
>> So we could write:
>>
>>> myFunc = anotherFunc $ case of
>>>                         Left err -> print err
>>>                         Right msg -> putStrLn msg
>>
>> A minor syntactical addition, a big win!
>
> +1.
>
> While we're on the topic, what do people think of a related problem,
> case expressions over monadic values?  I run into this often enough
> that it's a pain.  I'd like to take
>
>  result <- act1
>  case result of
>    ... -> actN
>
> and drop the bind entirely to get
>
>  case act1 of
>    ... -> actN
>
> I know that there are many helper functions and constructs to make
> this sort of thing more readable, but sometimes a case expression is a
> good fit and the preceding bind just ends up being noisy.
>
> --  
>  Jonathan Daugherty


I think your example is ambiguous in the sense that the case cannot  
know whether it should pattern match on the entire `m a' or just on  
the value `a' pulled out of the monad . Or maybe I don't entirely  
understand your example.

With the proposed `case of' it would become something like this:

   act1 >>= case of
     ... -> actN

Cheers,

Sebastiaan