Don wrote:
Lionello Lunesu wrote:
On 8-12-2009 1:43, Andrei Alexandrescu wrote:
Nice analysis. IMHO this should lead us to reconsider the necessity of
"^^" in the first place. It seems to be adding too little real value
compared to the complexity of defining it.
No, Don's just being awefully thorough. If you'd revisit all existing
operators with the same thoroughness you would probably give up the
whole idea of writing a language. Apart from the int/int division
there's the int<<int, "What if I shift more than 31?" "What if I shift
with <0?" and of course int+int "What to do on overflow?" etc..
I think ^^ can be made to work just fine. Let's not get carried away
trying to make it perfect.
L.
Exactly. The fallback case is to just make int^^int an int.
It's only because I was looking at the range propagation stuff inside
the compiler, that I got the idea that we could better than that. But,
as Andrei says, maybe it's just not worth any more thought at this stage.
Walter and I decided to leave the decision of ^^ up to you, Don. You are
the best positioned to make it. I hope you will piggyback a decision
about ^^= to it, too.
What I'd like would be a solid rationale for the choice. Off the top of
my head and while my hat is off to your math skills and experience, I
have trouble understanding the soundness of making int^^int yield an
int, for the following reason:
For all negative exponents, the result is zero, except when the base is
1 or -1. So I guess I'd suggest you at least make the exponent unsigned
- the result is of zero interest (quite literally) for all negative
exponents. If that behavior is interesting, it would be great if you
provided a rationale for it.
One small nit is that the exponential function is increasing very
rapidly, much faster than multiplication. So yielding a long may
actually be justified. (Some people would argue 32-bit multiplication is
in the same league and ought to yield 64-bit results.) But then again,
most uses of ^^ only raise things to small powers such as 2 and 3.
Anyhow, the power is yours - again quite literally :o).
Andrei
