On Friday, 22 February 2013 at 20:32:59 UTC, Jonathan M Davis
wrote:
On Friday, February 22, 2013 14:31:55 Steven Schveighoffer
wrote:
It is probably rare to have both a const and non-const
overload, that is
true, but it is not up to D to decide what design is best. We
should take
the most flexible approach, and allow designers to come up
with whatever
ideas they like. I don't think there is any significant extra
work
required to support const method overloads in the compiler, in
fact it
would be a more significant change to make that an exception.
A prime example of where overloading on const can be useful is
caching. You
can write a function which caches its result for efficiency
purposes, but the
const version can't cache, whereas the non-const one can. So,
you can do
something like
auto calculate()
{
if(_dirty)
_cache = _doCalculation();
return _cache;
}
auto calculate() const
{
if(_dirty)
return _doCalculation();
return _cache;
}
If you couldn't overload on const, then that wouldn't be
possible. You'd be
forced either to forgoe const and make it cache or to make it
const and forgoe
the caching.
Nothing prevent you from putting the cache outside the object.
