On Tue, 08 Feb 2011 11:49:47 -0500, spir <denis.s...@gmail.com> wrote:
On 02/08/2011 05:17 PM, Steven Schveighoffer wrote:
What is the difference between:
bool opEquals(T)(T y) if (is(T == BigRational)) {...}
and
bool opEquals(T)(T y)
{
static if(is(T == BigRational)) {...}
else static assert(0, "invalid type");
}
Thank you very much, Steven.
I'd say: in the first case, there are as many functions as constraints
variants (provided other variants are implemented, indeed) triggered by
actual calls to opEquals.
Tell me if i'm right on this: In the second case, there is a single
function generated, and branches of static if are inserted according to
actual calls. Is that right? If yes then I don't really care of this use
of static f (I'm aware there are other, maybe more relevant, use cases).
No, there are multiple functions generated, and in each function, the
correct static if branch is compiled. It's technically no different
code-generation wise than the constraint version.
The difference comes in the compiler decision of whether to compile a
function or not, and who is responsible for reporting the error (in the
first, the compiler reports the error, in the second, you are responsible
for reporting the error via static assert).
-Steve
