Am 25.07.2014 20:45, schrieb Jonathan M Davis:
On Friday, 25 July 2014 at 13:34:55 UTC, H. S. Teoh via Digitalmars-d
wrote:
On Fri, Jul 25, 2014 at 09:46:55AM +0000, Jonathan M Davis via
Digitalmars-d wrote:
Even worse, if you define opEquals, you're then forced to define
toHash, which is much harder to get right.
If you're redefining opCmp and opEquals, I seriously question whether
the default toHash actually produces the correct result. If it did, it
begs the question, what's the point of redefining opCmp?
Except that with the current git master, you're forced to define
opEquals just because you define opCmp, which would then force you to
define opCmp.
That sentence doesn't make much sense, did you mean "opHash just because
you define opEquals" or something similar?
opEquals is trivial. toHash is much harder to get right, especially if
you want a hash function that's even halfway decent.
As written before somewhere else, a toHash that is as decent as the
current default, but limited to the fields you actually want, should be
really easy, if phobos exposed a function like
hash_t createHash(T...)(T args)
that does to args what D currently does to all members to create the
default hash.
(I kinda tend towards "whatever, maybe not defaulting opEquals to
a.opCmp(b) == 0 is acceptable, people should stumble upon this when
first reading the documentation on how to overload operators" now, though)
Cheers,
Daniel
