opIndexAddAssign? ...

[Stewart Gordon]

Manfred Nowak Wrote:

> On writing the implementation of a map, where the Valuetype is a 
> set, I had to stop on recognizing, that only opIndexAssign is 
> permitted.

To add opIndexAddAssign et al would be a step back towards the old C++ nightmare of providing lots of operator overloads where just one should suffice.

> I.e.:
>     map[key]+= element;
> has no possible overload.
> 
> OpIndex delivers an rvalue and the only possibility to get an 
> lvalue is in conjunction with a plain assignment.
> 
> Why arbitrary restrictions when the goal is to have great 
> expressiveness?

I agree.  It's been said about properties enough times, and the same should apply to array indexes.  That is,

    qwert[yuiop] op= asdfg

should be, in the lack of any overriding alternative (such as an op<op>Assign on the type of qwert[yuiop]), equivalent to

    qwert[yuiop] = qwert[yuiop] op asdfg

except that qwert and yuiop are evaluated only once.

Stewart.