Re: [boost] Re: Policy-based vector? [was: Submission: Fixed-Capacity STL Containers Library]

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-02-06 20:04:41

At 07:33 PM 2/6/2002, mfdylan wrote:

 >--- In boost_at_y..., "Andrei Alexandrescu" <andrewalex_at_h...> wrote:
 >>
 >> I agree that a nicer default template argument mechanism (such as an
 >> exclamation mark meaning, "use the default here") would make things
 >better,
 >> but by and large, I don't consider this to be a problem.
 >>
 >Why exclamation mark?  Surely just omitting it entirely would be
 >preferable:
 >
 >my_vector<int,,range_checking> v;
 >
 >Is there any reason that would cause a parsing problem?
 >Personally I'd like to see this extended to function calls too.

One solution being discussed (used by many languages) is named parameters:

    my_vector<int, checking_policy=range_checking> v;

It works particularly well when you want to supply a non-default only for 
the last of a long list of arguments.

There is an open question as to whether it is acceptable to simulate 
named-parameters using template techniques, or they should be built into 
the language.

--Beman