Re: New members of functional.hpp

From: Daryle Walker (darylew_at_[hidden])
Date: 2000-09-08 00:04:35

on 9/6/00 8:30 PM, Mark Rodgers at mark.rodgers_at_[hidden] wrote:

> I was thinking of adding something like
> 
> template <class Arg1, class Arg2 = Arg1, class Result = Arg1>
> struct plus : std::binary_function<Arg1,Arg2,Result>
> {
>   Result operator()(typename call_traits<Arg1>::param_type x,
>   typename call_traits<Arg2>::param_type y) const
>   {
>       return x + y;
>   }
> };
> 
> template <class Arg1, class Arg2 = Arg1, class Result = Arg1>
> struct minus : std::binary_function<Arg1,Arg2,Result>
> {
>   Result operator()(typename call_traits<Arg1>::param_type x,
>   typename call_traits<Arg2>::param_type y) const
>   {
>       return x - y;
>   }
> };
> 
> to functional.hpp.  The idea would be to allow things like
> 
> boost::plus<Foo*,std::ptrdiff_t,Foo*>()
> or   boost::minus<Foo*,std::ptrdiff_t,Foo*>()
> or   boost::minus<Foo*,Foo*,std::ptrdiff_t>()
> 
> as well as the traditional
> 
> boost::minus<int>()
> 
> Thoughts anyone?

I like it.  I like it so much that I've already put a preliminary version,
with new documentation file, in the Boost vault.  They are under the
"dlw_functional" folder.

I've been wishing for classes like this for several weeks, but with another
operator (not in the standard list).  I guess your post got me to start
doing it myself.  I think for the next version I'll add the other extensible
operators (like << delete , [] =), then most of the remaining operators.

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