Operator overloading -- lets collect some use cases

[Chad J]

Don wrote:
> 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.
> 

Array-alikes/Containers.

dstring (okay, mtext now, damn new aliases *grumble grumble*)
http://www.dprogramming.com/mtext.php

Call chaining.
http://www.dsource.org/projects/tango/docs/current/tango.io.Stdout.html
Notice the `Stdout ("abc") ("def") (3.14);  => abcdef3.14`

Hybrid uses opCall and opIndex to do some of its fancy stuff.