aarti_pl wrote:
Don pisze:
There's been some interesting discussion about operator overloading
over the past six months, but to take the next step, I think we need
to ground it in reality. What are the use cases?
I think that D's existing opCmp() takes care of the plethora of
trivial cases where <, >= etc are overloaded. It's the cases where the
arithmetic and logical operations are overloaded that are particularly
interesting to me.
The following mathematical cases immediately spring to mind:
* complex numbers
* quaternions (interesting since * is anti-commutative, a*b = -b*a)
* vectors
* matrices
* tensors
* bigint operations (including bigint, bigfloat,...)
I think that all of those are easily defensible.
But I know of very few reasonable non-mathematical uses.
In C++, I've seen them used for iostreams, regexps, and some stuff
that is quite frankly bizarre.
So, please post any use cases which you consider convincing.
DSL support in mother language. As an example I can give SQL in D or
mockup tests description language (usually also in D - not as a separate
script language).
Could you be more specific about this? For SQL, arithmetic and logical
operators don't seem to be involved. The example you gave showed (if I
understand correctly) a wish to make expression templates involving
comparison operators, a task which is currently impossible.
I also found your first example a little too simple.
Query query = Select(a).Where(id == 5);
I presume you would also want to do things like:
for(int i=0; i<10; ++i) {
Query query = Select(a).Where(id == (arr[i+2] + func(i)) || id==78+i);
...
}
meaning you'd also need to overload && and || operators.
Is that correct?
In my previous posts I already put few arguments why it is sometimes
much more handy to use "DSL in mother language" approach rather than
string mixins with DSL language itself.
Still, that doesn't necessarily involve operator overloading. I really
want to assemble a list of cases which do.
