On Tuesday, 4 February 2014 at 17:17:13 UTC, Adam D. Ruppe wrote:
On Tuesday, 4 February 2014 at 17:09:02 UTC, Gary Willoughby
wrote:
What does the alias attribute do here:
void foo(alias bar)
This specifically won't compile, alias params are only allowed
in a compile-time list. So
void foo(alias bar)() { ... }
would work.
Anyway, what it does is you pass another symbol to the
function/template and the alias parameter works as the same
thing. So let's play with:
void foo(alias bar)() {
import std.stdio;
writeln(bar);
}
void main() {
int a = 20;
foo!a(); // will print 20
}
What happened is foo!a passed the /symbol/, not just the
variable contents, the variable itself, as the alias parameter.
An important difference between this and a regular int
parameter is you can assign to it too:
void foo(alias a)() {
import std.stdio;
writeln(a);
a = 50; // this is as if we literally wrote cool = 50;
in main()
}
void main() {
int cool = 20;
foo!cool();
assert(cool == 50); // passes
}
alias parameters differ from regular parameters because a
regular parameter can only be a type name. An alias parameter
can be another variable.
You can also pass it functions and call them as if the user
wrote the call themselves - no pointers/delegates involved.
Ah great, thanks that makes perfect sense.
