Recursive template expansion

[Philippe Sigaud]

On Mon, Mar 1, 2010 at 10:16, Norbert Nemec <Norbert at nemec-online.de> wrote:

>
> Is there any fundamental error in my thinking? Some simple
> misunderstanding? Some slightly different syntax to be used? Or is it simply
> an unnessessary restriction in the compiler that could easily be removed?
>

I don't know. Using factory functions, it seems to work and it has the nice
side-effect of simplfying the syntax (templated functions do all the type
deducing):

import std.stdio;

struct Sum(A,B) {
   A a;
   B b;

   auto opAdd(T)(T a) { return sum(this,a); }
}


struct Base {
   auto opAdd(T)(T a) { return sum(this,a); }
}

Sum!(A,B) sum(A,B)(A a, B b) { return Sum!(A,B)(a,b);}
Base!(A,B) base(A,B)(A a, B b) { return Base!(A,B)(a,b);}

void main() {
   Base a,b,c;

   auto d = a+b;
   writeln(typeof(e).stringof); // Sum!(Base, Base)
   auto e =de+a;
   writeln(typeof(f).stringof); // Sum!(Sum!(Base, Base),Base)
   auto f = e+e+d;              // Look Ma, no parenthesis
   writeln(typeof(g).stringof); // Sum!(Sum!(Sum!(Sum!(Base,Base),Base),
Sum!(Sum!(Base,Base),Base)),Sum!(Base,Base))
}


Cheers,

  Philippe
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