On Wednesday, 21 September 2016 at 19:01:40 UTC, Timon Gehr wrote:
There is no technical reason that would make the implementation
of this feature difficult, if that is your question.
Basically, the rationale is: external operators cannot be used
in generic code that does not import the module defining the
operators. C++ works around this using ADL. Walter
(justifiably) does not like ADL, hence the limitation.
(I don't agree with that line of reasoning: obviously this is
not only an issue for operators, but for any UFCS function;
operators are mere syntactic sugar.)
The greatest offender I've found is how in phobos, arrays do not
behave as ranges without importing the module defining their
range operations.
Which I think is obnoxious, and maybe there's a solution to make
both cases less so, but I definitely don't think it's an argument
for exclusion.
