putting more smarts into a == b
Robert Jacques
sandford at jhu.edu
Sat Sep 26 20:45:54 PDT 2009
On Sat, 26 Sep 2009 21:32:13 -0400, Andrei Alexandrescu
<SeeWebsiteForEmail at erdani.org> wrote:
> Consider two objects a and b with a of class type. Currently, the
> expression a == b is blindly rewritten as a.opEquals(b). I argue it
> should be rewritten into a call to an (imaginary/inlined) function
> equalObjects(a, b), with the following definition:
>
> bool equalObjects(T, U)(T a, U b) if (is(T == class))
> {
> static if (is(U == class))
> {
> if (b is null) return a is null;
> if (a is null) return b is null;
> }
> else
> {
> enforce(a !is null);
> }
> return a.opEquals(b);
> }
>
> This hoists the identity test outside the opEquals call and also deals
> with null references. What do you think?
>
>
> Andrei
I like this. I think optimizing away opEquals for identical objects would
also be a good idea:
static if (is(U == class))
if(a is b || a is null || b is null) return a is b;
else
enforce(a !is null);
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