How to define templates

[Steve Teale]

Jarrett Billingsley Wrote:

> On Sun, Mar 29, 2009 at 1:46 PM, Steve Teale
> <steve.teale at britseyeview.com> wrote:
> > The documentation says:
> >
> > TemplateDeclaration:
> >        template TemplateIdentifier ( TemplateParameterList ) Constraint(opt)
> >                { DeclDefs }
> >
> > DeclDefs as defined where?
> 
> http://www.digitalmars.com/d/2.0/module.html
> 
> > What should be the effect of the following?
> >
> > import std.stdio;
> >
> > template gnomeSaying(T, U, V, string s)
> > {
> >    writefln(s ~ " motherfucker");
> > }
> 
> An error, since a function call is not a DeclDef.

OK, I didn't look there - perhaps a definition in 'Decalrations' would make thing easier.

But then I wonder, since a plain old string is acceptable as a template parameter, why I can't use a statement that does not involve any of the other template arguments.

Also, would it be reasonable for the compiler to issue a warning or error message to the effect that T, U, and V were never mentioned in the template body.

What is the basic difference between Templates and Macros - the declarations thing is obviously crucial, but why?