Re: Why no mod function?

Yes, that's pretty much what I did.  But surely such an important function
as mod should be available without having to write it yourself?

-Alasdair

On 7/10/07, Bill Page <[email protected]> wrote:
>
> On 7/9/07, Alasdair McAndrew wrote:
> > Why is there no modulus function in Axiom?  Such as
> >
> > -13 mod 10 producing 7.
> >
> > There's rem, but if you want a positive value you have to tweak the
> result.
>
> I guess you are looking for a function of the following type?
>
>   mod: (Integer, PositiveInteger) -> Integer
>
> > I can get x mod n with (x::ZMOD n)::INT but that's a bit of a kludge,
>
> To the best of my knowledge that is how one might be expected to write
> it in the Axiom interpreter. This emphasizes the notion of ZMOD(n) as
> a type
>
> (12) -> mod(i,n) == i::ZMOD(n)::Integer
>                                                          Type: Void
> (13) -> mod(-13,10)
>    Cannot compile conversion for types involving local variables. In
>       particular, could not compile the expression involving :: ZMOD #2
>
>    AXIOM will attempt to step through and interpret the code.
>
>    (13)  7
>                                             Type: PositiveInteger
>
> The problem here is that ZMOD(n) is not a type *constant*. This is ok
> in the Axiom interpreter but not in the Spad or Aldor compilers.
>
> > and if I put it in a program the compiler doesn't like it.
> >
>
> I would suggest that in Spad you should programming something like
>
> (24) -> mod(i,n) == (i>0 => i rem n; n + (i rem n))
>    Compiled code for mod has been cleared.
>    1 old definition(s) deleted for function or rule mod
>                                                           Type: Void
> (25) -> mod(-13,10)
>    Compiling function mod with type
>        (Integer,PositiveInteger) -> Integer
>
>    (25)  7
>                                             Type: PositiveInteger
>
> If you need help with this just let me know.
>
> Regards,
> Bill Page.
>

_______________________________________________
Axiom-mail mailing list
[email protected]
http://lists.nongnu.org/mailman/listinfo/axiom-mail