Operator overloading, structs

[dsimcha]

== Quote from bearophile (bearophileHUGS at lycos.com)'s article
> Yigal Chripun:
> > why not just use (i != 0) in both cases?
> Yes, here it can be done (if Don has implemented opEquals(int y)), but you don't
need that once you have something like opBool.
> > conversion of ints to bools in C is IMO a hole in the type system due to
> > the lack of a boolean type in C. All those narrowing implicit casts
> > inherited from C are a bad idea IMO.
> Walter was right, converting a generic integral to bool requires some time, that
in the middle of the the nested loop can slow down code a bit (5%, in a case of mine).
> A standard opBool method allows you to tell when a collection is empty, like an
empty string, an empty range, an empty array, and so on. you can use it instead of
somecollection.isEmpty().
> Java as Pascal keep booleans and integers separated, this looks tidy and clean.
I love clean things, but in practice I don't think the current design of D (and C,
Python, and several other languages) leads to a significant amount of bugs. It
seems one of those situations where practical considerations win over purity.

For D and other close to the metal languages, IMHO the int-bool relationship
should stay the way it is simply because that's the way it works on the bare metal
(at least on x86, for example, instructions like jz).  I think this is a good rule
of thumb in a close to the metal language, and even in the general case:  When in
doubt, do the thing that gives the user the least obstructed view of how things
"really" work at the next lower level.  This avoids lots of silly abstraction
inversions (One of which is building a strong boolean type on top of an int).