Template type parameters with their own type parameters

Peter Lundgren lundgrpb at rose-hulman.edu
Sat Mar 5 20:42:17 PST 2011


== Quote from spir (denis.spir at gmail.com)'s article
> On 03/05/2011 04:02 AM, Peter Lundgren wrote:
> > I have a function that I think should look something like this:
> >
> > MyStruct!T myFunc(T)(MyStruct!T x, ...) {
> > 	...
> > 	return MyStruct!T(...);
> > }
> >
> > and the closest I can get to is:
> >
> > T myFunc(T)(T x, ...) {
> > 	...
> > 	return T(...);
> > }
> >
> > which works, but doesn't make clear the intended use and gets in the way of
> > overloading. How can I express the intent of the first version.
> Maybe I do not exactly understand your problem; anyway, the following runs fine
> by me:
> struct S (T) {
>      T v;
> }
> S!T inc (T) (S!T s) {
>      return S!T(s.v + 1);
> }
> unittest {
>      auto s1 = S!int(1);
>      auto s2 = inc(s1);
>      assert ( s2.v == 2 );
> }
> Could you provide (1) context (2) example (3) errors?
> Denis

Thanks for the help. I'd convinced myself that it didn't work and missed the
actual problem. I was mixing template type and template value parameters. What I
really wanted was this:

MyStruct!v myFunc(string v)(MyStruct!v x, ...) {
 ...
 return MyStruct!v(...);
}


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