WAT: opCmp and opEquals woes
Daniel Gibson via Digitalmars-d
digitalmars-d at puremagic.com
Fri Jul 25 03:27:27 PDT 2014
Am 25.07.2014 12:07, schrieb Jonathan M Davis:
> And once you define opEquals, you have to define
> toHash. So, what you're suggesting would force a lot more code to define
> toHash, which will likely cause far more bugs than simply requiring that
Is it actually hard to define toHash, or should it be?
What is done by default? I guess some magic hash is built over all
members of a type (like all members are compared in opEquals).
So couldn't there be some templated function that creates the hash for
you in the same way as it's done now, but only for the values you want
to hash?
e.g.
hash_t createHash(T...)(T args) {
return (do magic with args);
}
struct Foo {
int x;
int y;
string str;
int dontCare;
bool opEquals()(auto ref const Foo o) const {
return x == o.x && y == o.y && str == o.str;
}
hash_t toHash() {
return createHash(x, y, str);
}
}
Cheers,
Daniel
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