Re: Template function as argument to another template function

From: Nicolas Pavlidis (pavnic_at_sbox.tugraz.at)
Date: 10/07/04 

Date: 07 Oct 2004 19:38:57 +0200

Nicolas Pavlidis <pavnic@sbox.tugraz.at> writes:

> Jim West <eggplantparts@yahoo.com> writes:
>
> > The following code compiles and executes properly on one compiler
> > (GNU C++) but not on another (Intel C++ V8.1). Which compiler is
> > correct? If my code is improper (that is, the Intel compiler is
> > correct), is there an appropriate way to do what I'm trying to do?
> >
> >
> > template <class T>
> > T FOO(const T &a) { return a; }
> >
> > template <class T>
> > T BAR(T (*f)(const T &b), const T &c) { return f(c); }
> >
> > int main() {
> > double x = 10.0;
> > double y = BAR(FOO, x);
> > }
>
> IMHO intel is "more correct", you want to call BAR this way:
>
> double y = BAR(FOO<double>, x);
>
> Then intel will must not make any problems.
>
> As you see intel needs a real instantiation of the templated function,
> maybe g++ finds the correct type by itself.

g++ is a bit more inteligent :-). It makes the folowing (I think that it
soes after analysing your code) :

The jole is that every instantiation of foo may fit the requirement for
the functionpoiunter in the paramlist for bar, so this is no problem for
g++, the real instatiation of foo is generated while instatiating bar in
main().

intel needs a real function for passing a functionpointer, so the
exlpicit instantiation is necessary, which is a problem for the MSVC -
compilers :-).

Kind regrads,
Nicolas 

-- 
|     Nicolas Pavlidis       |       Elvis Presly:    |\ |__      |
|   Student of SE  & KM      |      "Into the goto"   | \|__|     |
|  pavnic@sbox.tugraz.at     |       ICQ #320057056      |        |
|-------------------University of Technology, Graz----------------|

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