[Aldor-l] Generators (destructuring cross)

[Bill Page]

On 07 Nov 2007 19:47:42 +0100, Martin Rubey <martin.rubey at univie.ac.at> wrote:
> Dear Peter, Francois,
>
> well, I had to try it, and I'm quite amazed.  It's beautiful.
>
> It does not work for dependent crosses, but that's probably too much too ask
> for, as the compiler doesn't like them too much...
>

Maybe this alternate coding helps to explain why it doesn't and
perhaps why we should not expect it to work for dependent crosses ('a'
is not constant in this scope):

#if DoesntCompile
       stdout << "test dependent:" << newline;
-- Cross(n: MachineInteger, SmallPrimeField n)
       for (a:MachineInteger, b:SmallPrimeField a) in g repeat {
               stdout << a << " " << b << newline;
       }
#endif


root at sage:~/aldor-src/aldor/install/aldor# aldor -fx  -lalgebra
-laldor -DWantRuntimeError -DDoesntCompile crossiterator.as
"crossiterator.as", line 63:
       for (a:MachineInteger, b:SmallPrimeField a) in g repeat {
............^
[L63 C13] #1 (Error) `a' is used in a type, so must be constant, and
so cannot be assigned to.

Regards,
Bill Page.