Thanks, Philippe, for the elegant workaround!
Still I would like to know the reason for my original failure,
especially since the compiler error message did not contain any line
number whatsoever. Getting this kind of error message in a large project
must be really ugly to solve, even if the workaround is so
straightforward...
Philippe Sigaud wrote:
On Mon, Mar 1, 2010 at 10:16, Norbert Nemec <[email protected]
<mailto:[email protected]>> 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
