On 09/10/13 17:50, Daniel Davidson wrote:
Take, for example, LinearCongruentialEngine from random.d. It has a function:
bool opEquals(ref const LinearCongruentialEngine rhs) const
Why is it using const here instead of immutable?
Among other things, because no LinearCongruentialEngine will ever, ever be
immutable -- because it won't work if it's immutable. Whereas ref const I
believe is simply saying, "You can't mutate it via this reference." I'm not
sure if it ought technically to be auto ref const.
In any case, I think the general reason is in order to be agnostic about type
qualifications. Try:
BigInt a = BigInt(5);
immutable BigInt b = immutable(BigInt)(5);
writeln(a.opEquals(b));
... which works. BigInt.opEquals takes input by an auto ref const.
