On Friday, 25 July 2014 at 10:27:27 UTC, Daniel Gibson wrote:
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?
Sure. We could create something like that, and we probably
should. It would help out in cases where the default wasn't
appropriate (e.g. only some of the member variables were part of
opEquals). But why force folks to define opEquals and toHash when
the defaults would have worked fine for them just to fix the code
of folks who didn't make the effort to test that opEquals and
lhs.opCmp(rhs) == 0 were equivalent? That seems to me like we're
punishing the folks who actually write good code and test it in
order to help those who don't even test the basic functionality
of their types.
- Jonathan M Davis
