programming, using op(), was ..RE: Bugfix for GosperSum? (was: cannot load Zeilberger)

El s?b, 06-01-2007 a las 18:27 -0700, Robert Dodier escribi?:
> On 1/6/07, Richard Fateman <fateman at cs.berkeley.edu> wrote:
> 
> > Also, be aware that op()  takes a fair amount of time and space,
> > since it formats its argument.
> 
> If op is a bottleneck for many programs, we should work on
> speeding up nformat then. Better than than to tell every user
> to use a more obscure alternative.
> 
> > Else  case(inpart(expr,0),
> >            ["+", yyy],
> >            ["*", zzz],
> >            [otherwise, ...])
> 
> I'm not opposed to having a case statement, but I don't like
> constructs that don't distinguish the different parts.
> I don't think a list of 2-element expressions has anything to
> recommend it, except it would be easy to implement.
> 
> Better would be something more explicit like
> 
>   FOO (expr, case "+" : yyy, case "*" : zzz, otherwise : ...)

I vote for something like

case(expr,
       "+", xxx,
       "*", yyy,
       otherwise, zzz)

There are other situations in Maxima ('depends', for example) where the
meaning of an argument depends on its position in the arguments list.

-- 
Mario Rodriguez Riotorto
www.biomates.net