On 5/3/12, Joe Groff <arc...@gmail.com> wrote:
> However, it appears that (m1,m2,...)&|@:^ doesn't get the same
> treatment and falls back to power-then-residue, causing it to blow up
> for large exponents:
>
> ---
> 5 7 11 (10 14 22&|@:^) 400 4000 40000
> |NaN error
> | 5 7 11 (10 14 22&|@:^)400 4000 40000
> ---
Here's an alternative.
powmod =: 1 :(':';'(m|*)/(|.|:b)^~(m|*:)^:(<#{.b=.#:y) x')
5 7 11 (10 14 22 powmod) 40 4000 40000
5 7 11
Note that this is fully array-based, I never explicitly iterate on the
values. This is, however, also a disadvantage as if one of the powers
is much greater than the others then I'll do some unnecessary extra
computation.
This might of course be slower than calling the special code for each
modulus separately the way Raul Miller has recommended.
Ambrus
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