Re: [boost] painless currying

Subject: Re: [boost] painless currying
From: Larry Evans (cppljevans_at_[hidden])
Date: 2011-09-03 09:38:05

On 09/03/11 08:28, Larry Evans wrote:
[snip]
> With the 2 attached files (compiled with gcc4.6 and with boost trunk
> [which svn update showed was revision 74198]), the output is:
> 
[snip]
> which shows several copy CTOR's executed.  These copy CTOR
> calls were caused by the code like this:
> 
>   curryable (Fun f, Arg0 a0, Arg1 a1, Arg2 a2):
>   fun (f),
>   arg0 (a0),
>   arg1 (a1),
>   arg2 (a2)
>   {
>   }
> 
> produced by the BOOST_PP code.  Is there any way to prevent
> these copies, maybe by declarations like:
> 
>   Arg0 const&
>     arg0;
> 
> instead of the existing:
> 
>   Arg0
>     arg0;
> 
> ?
> 
[snip]
OOPS.  I should have thought a bit more.  The reason:

  Arg0 const& arg0;

won't work is because the arguments to the curryable CTOR:

  curryable (Fun f, Arg0 a0):

maybe be gone by the time f is actually called, and that's
why they have to be copied.

Sorry for noise :(

-Larry