Re: [boost] Interest in a tweener library

Subject: Re: [boost] Interest in a tweener library
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2012-07-16 07:50:43

Julien Jorge wrote:
> Le Sun, 15 Jul 2012 13:37:06 +0200,
> Klaim - Joël Lamotte <mjklaim_at_[hidden]> a écrit :
>
> > Did you consider copying the value instead of keeping a
> > reference to it? Also, what do you think about allowing the
> > user to use one or the other?
>
> Sorry I made a mistake in the code that results in a
> misunderstanding.
> The argument of the function g() should not be a reference:
>
>   void g( boost::function<double (double)> func )
>   {
>     double t = /* … */;
>     double d = func( t );
>     // …
>   }
>
>   int main()
>   {
>     g( &f );
>   }
>
> Thus, it is a copy of the function object. There is no reason
> to keep a reference to the boost::function here.

From what you've posted, there's no need to copy the boost::function object.

Anyway, if g() were a function template, then the compiler could inline the call to f():

double
f()
{
   // ...
}

template <class F>
void
g(F _function)
{
   double const t(/*...*/);
   double const d(_function(t));
   // ...
}

int
main()
{
   g(f);
}

_function(t) would actually be f(t), with no boost::function object, and it could be inlined.  That, however, requires that the caller create boost::function objects when those are needed to bind arguments, including this pointers.

If g() would be bloated because most of the code is not dependent on F, then factor out code before and after calling the function argument into non-template helper functions called by g().

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer                     using std::disclaimer;
Dev Tools & Components
Susquehanna International Group, LLP  http://www.sig.com





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