[boost] Re: call_traits aka parameter_traits

From: Howard Hinnant (hinnant_at_[hidden])
Date: 1999-11-29 11:47:13

Beman Dawes wrote on 11/29/99 10:23 AM
>Unless I am misunderstanding you, that would cause a reference to a
>reference, which is not allowed by the language rules.

I was just talking about changing the value of by_value, nothing more.  
As good example uses have yet to be proposed for by_value, I was probably 
premature to suggest the change.

>That was the
>case that caused Steve Cleary to develop the empty_member constructor
>argument workaround that eventually morphed into call_traits.

I think I got excited about call_traits for the wrong reason 
(optimization).  I think the true value is exactly what you're stating 
here (avoidance of reference to a reference).  And also if it can help 
with the Dietmar/make_pair dance.

If I'm right about the optimization part, then that means that the list 
of bool, char, short... is superfluous.  It doesn't hurt, but call_traits 
is just as good without the "by_value" specializations for the built-in 
types.

Then again, the answer to the optimization part my vary from platform to 
platform.  I'm not sure. (so let's defintely leave it in so we can 
explore that!)

-Howard