Re: [boost] painless currying

Subject: Re: [boost] painless currying
From: Larry Evans (cppljevans_at_[hidden])
Date: 2011-08-26 17:51:13

On 08/26/11 15:24, Dave Abrahams wrote:
> 
> on Fri Aug 26 2011, Larry Evans <cppljevans-AT-suddenlink.net> wrote:
> 
>> Since an n-dimensional array can be thought of as a function of
>> n indexes, I would think then that subscripting multi-dimensional
>> arrays would rub you the wrong way:
>>
>>   int f[1][1][1];
>>
>>   f[0] => doesn't return an int
>>   f[0][0] => doesn't return an int
>>   f[0][0][0] => *does* return an int
>>
>> Instead, would you prefer the following symmetrical version?
>>
>>   f[0] => doesn't return an int
>>   f[0][0] => doesn't return an int
>>   f[0][0][0] => doesn't return an int
>>   f[0][0][0]() => *does* return an int
> 
> No, sorry, but that's just silly.  Array indexing is entirely
> consistent:
> 
>    f[0] => returns int(&)[1][1]
>    f[0][0] => returns int(&)[1]
>    f[0][0][0] => returns int&
> 
Then so is (using haskell notation):

  f :: X -> Y -> Z -> int

  f x => returns Y -> Z -> int
  f x y => returns Z -> int
  f x y z => returns int

which is Eric's point.  IOW, when supplied with enough arguments,
the function returns the result_type of the function, just as,
when a multi-dimensional array is supplied enough arguments
(or indices) it returns the value type of the array.

-Larry