On 12/14/10 2:23 AM, Walter Bright wrote:
bearophile wrote:
Andrei:
D's constrained templates were introduced on 17 June 2008 and they've
been
a smashing hit. Virtually all of Phobos uses them, and I'm sure a lot of
generic client code. They take half a minute to explain and solve a
difficult problem in a very simple manner.<
A template with two constrains makes it less handy to add error
messages that
explain why the instantiation has failed:
Adding such error messages misses the point of constraints. The idea is
that template overloading is based on constraints. Given 3 templates
with 3 constraints, overload resolution picks the one with constraints
that pass. Giving error messages for the others is wrong.
If you want it to produce error messages if the instantiation is wrong,
the correct way is to use static asserts within the template body. No
additional features serve any purpose.
Yah, I was planning on writing the same response.
Andrei
