foreach, an analogy

[Bill Baxter]

I like analogies, so here goes one.  If you don't just skip it.  :-)

Say you've built a house and you're almost done, but you find one 
doorway with a door that's about an inch too narrow for the frame. 
You'd really like to cover that gap somehow.  You could just leave it 
as-is.  Sure.  You've got *most* of the doorway covered after all.  It's 
not like a criminal could sneak in through a one-inch gap.  Still, it 
could get pretty cold in the winter, so you'd really like to fix it.

Clearly the best solution long term is to get a bigger door.

But you don't have a bigger door.  You do, however, have a clever 
solution: take another door, identical to the first, and hang it on the 
*other side* of the frame to cover the gap.  Perfect!  The gap is covered!

But hmm.  Now there are two doors.  Either of them alone *almost* enough 
to cover the doorway.  You don't really _need_ two doors doing almost 
exactly the same thing.

It's not so bad, though.  At least in the summer, when you don't need 
it, you can just leave that second door open and out of the way. Even 
take it off its hinges and put it in the basement.

That second door, as I'm sure you've figured out, is foreach_reverse.

And really I do believe it's not so bad.  It's an ugly hack, like 
hanging a second door to fill a small gap, but if you don't want to 
iterate backwards over arrays as fast as possible, then you're free to 
ignore it, put that door in the basement, and use whatever technique you 
prefer.

However, I still hope the plan is to one day get a bigger door.

--bb