[vox-tech] grokking g++ errors

[Peter Jay Salzman]

On Thu 02 Feb 06,  1:12 PM, Micah J. Cowan <micah at cowan.name> said:
> On Thu, Feb 02, 2006 at 02:59:35PM -0500, Peter Jay Salzman wrote:
> > On Thu 02 Feb 06, 10:21 AM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us> said:
> > > 
> > > You didn't ask for assistance in actually troubleshooting this problem, but
> > > templates traditionally must be defined before they are instantiated in the
> > > source.  It is possible that newer compilers can handle definition after
> > > instantiation, but I don't know how they do it.
> > 
> > Sorry for being so dense, but I'm just now starting to try to really learn
> > function and class templates.
> > 
> > Do you mean that the template function definition must be seen before the
> > any calls to the function is made (I assume that's the instantiation)?
> > 
> > I guess what I'm asking is -- is the template function's prototype not
> > enough?  The actual definition must be seen before any calls to the function
> > are made?
> 
> IIRC this should not be true (though I'll point out that in your sample
> code, no such prototype has been provided);

it was a code snipppet -- the prototypes were in an include file that i
didn't show!   :)

> Realize that defining a function /template/ does not define any
> function, only a template.  That's what /instantiating/ the template
> does. It makes it easy on the compiler if the function template's
> definition is in scope at the time you implicitly or explicitly
> instantiate it, and some compilers may require this, though the C++
> stnadard does not (only that it's in the same "translation unit"
> somewhere).
 
that's definitely a good way of putting it -- thanks!  i'll keep that in
mind.

pete