Re: [pure-lang-users] Swapping Symbols and Integers

[David B. <dh...@gm...>]

On Fri, Aug 8, 2008 at 3:30 AM, Albert Graef <Dr....@t-...> wrote:
> So something like this should do the job in Pure:
>
> a*b::int = b*a if varp a;
> x*a*b::int = x*b*a if varp a;
>
> (In addition, you'll probably need some associativity rules to make this
> work in the general case.)

Excellent, thanks!  I finally got your suggestion to work in Pure.
(Took awhile because I had to work around having multiple versions of
LLVM installed though so that pure-0.4 would build).

I also got it to work in Q:

    A * B:Int = B * A if isvar A;
    X * A * B:Int = X * B * A if isvar A;
    A * (B * C) = A * B * C;

Then, I can ask it to reduce an expression like:

    ==> 3 * ((A * 2) * 4)

and I get:

    24*A

-David