On Wed, 18 Nov 2009 14:50:42 +0300, Bill Baxter <[email protected]> wrote:
On Wed, Nov 18, 2009 at 3:36 AM, retard <[email protected]> wrote:
Wed, 18 Nov 2009 03:31:11 -0800, Bill Baxter wrote:
On Wed, Nov 18, 2009 at 3:16 AM, retard <[email protected]> wrote:
Wed, 18 Nov 2009 03:10:57 -0800, Bill Baxter wrote:
Didn't this used to work?
template factorial(int i) {
enum factorial = (i==0) ? 1 : i*factorial!(i-1);
}
With DMD 2.036 I'm getting:
Error: template instance factorial!(-495) recursive expansion
Seems like it expands both branches regardless of the condition. And
seems to me like it shouldn't.
There's probably a confusion here. It evaluates lazily the value of
factorial!(), but its type (which happens to be infinitely recursive
must be evaluated eagerly in order to infer the type of the ternary
op.
That makes sense. I guess the ?: op is defined to do that in all
cases.
Might be nice though if it didn't do that in cases where the condition
was statically known.
so
int foo = (1==1) ? 6 : "haha";
would work, too? I think it would still need to check that the types of
both branches match.
Yeh, that could be confusing.
Actually it would break a lot of code, too, now that I think of it.
People use typeof(true?a:b) to get the common type.
That's why it probably needs to be a distinct thing, a static ?:.
--bb
The simplest solution is probably to give the compiler a hint:
enum foo = someStaticCondition ? cast(Foo)SomeTemplate!() :
cast(Foo)SomeOtherTemplate!();
Looks a bit hackish (and doesn't currently work), though.
