Re: Modulo (for complex)

[Asko Kauppi <askok@...>]

How should the % operator be defined for complex numbers, then?  :)

Off the LNUM patch:
<<
/* Complex modulus:
*
* C99 does not provide modulus for complex numbers. We should at least
* give an error here.
*/
lua_Complex luai_vectmod( lua_Complex a, lua_Complex b )
{
    return luai_nummod( creal(a), creal(b) ) + luai_nummod( cimag 
(a), cimag(b) ) * I;
}
<<


Doug Currie kirjoitti 4.10.2007 kello 4:51:

> On Wednesday, October 03, 2007 Miles Bader wrote:
>
> > So it seems like David's almost certainly right:  since they couldn't
> > use the underlying % operator, they just used the "equivalent  
> > formula",
> > "a - b * floor (a / b)", and that gives a slightly different  
> > result than
> > the C integer operator on typical hardware.
>
> Yes, the point is that in programming languages we want to have
> matched pairs of "quotient" and "remainder" operations such that
>
> if
> q = quotient(a,b)
> r = remainder(a,b)
> then
> a = b * q + r
>
> Lua's % and math.floor make such a pair.
>
> An excellent comparison of some choices in this space is
> http://portal.acm.org/citation.cfm?id=128862&coll=portal&dl=ACM
> which is summarized at
> http://en.wikipedia.org/wiki/Modulo_operation
>
> e
>
> --
> Doug Currie
> Londonderry, NH, USA