Make opAssign return ref

[Bolpat]

Assignment should return the assigned object and not be void. The example is misleading.

[AndrejMitrovic]

That's not true at all. Where are you getting this from?

[Bolpat]

Where are you getting this from?

From my experience with all C-like languages I know. One can always do x = y = z (except for no-copy types) and if ((a = f()) == b) { } for built-in types and usually for user defined types. I've been taught to define assignment to work like this and never different.

Maybe I've said it wrong. The result of assignment is (a reference to) the lvalue after being assigned to (and not the value being assigned as one could interpret the term assigned object). It should not be void. At least in Ali Çehreli's Book it is the assigned lvalue, but not a reference to it which is an error from what I know.

When I read the example the first time, I concluded the D compiler made the return this and ref implicit.

That's not true at all.

Give me a proper counterexample. Where is it useful not to return the lvalue after being assigned to?

I've taken a look through Phobos and found Nullable's opAssign that returns void. I also found BigInt's opAssign that does return BigInt. At least BitFlags's opAssign returns ref sometimes.

Interestingly, any C++ course teaches to define assignment as my_type& operator=(...) but in D this seems not to be the case. I'd really like to understand the reason to it, so I've asked this in the Forum.

[AndrejMitrovic]

Returning ref can be useful for chaining assignments, sure. But it's not an actual requirement.