more flexible partial application

[John Hughes]

>On 1/23/06, Sebastian Sylvan <sebastian.sylvan at gmail.com> wrote:
>  
>
>>Are there any subtle reasons for why something like the following
>>couldn't be allowed?
>>
>>
>>    
>>
>>>foo x y z w = ...
>>>bar x w = foo x _ _ w
>>>      
>>>
>>I.e. a more flexible version of partial application. This would be
>>translated too
>>
>>    
>>
>>>bar x w = \y z -> foo x y z w
>>>      
>>>
>>I.e a function which takes the "_" parameters in the same order they
>>were encountered in the function application.
>>
>>    
>>
I'd be against this--its semantics isn't clear enough to me. For example,
I usually assume id e = e, for any e, but

    id (f _ x) y  =  id (\y->f y x) y = f y x
    /=
    f _ x y = \z -> f z x y

Or would (f _ x) y and f _ x y maybe be different? That would fix the
problem above, while introducing another. Please, no!

John