you could do this:
matchdeclare([a,b,c,d],any);
f[Interval(a,b),Interval(b,c)):=fInterval(a,b,c,d)
now define fInterval...
etc.
Richard Hennessy wrote:
> I think you have to define f(x,y) as
>
> f([v]):=
> block(
> if length(v) = 2 then
> if not freeof('Interval,first(v)) and not freeof('Interval, second(v)) then
> Interval(min(a*c,a*d,b*c,b*d),max(a*c,a*d,b*c,b*d))
> else
> first(v) * second(v)
> else
> error("Function takes two arguments")
> )$
>
> ----- Original Message -----
> From: "Sheldon Newhouse" <sen1 at math.msu.edu>
> To: <maxima at math.utexas.edu>
> Sent: Thursday, June 04, 2009 9:40 PM
> Subject: parsing arguments for functions
>
>
> Hello,
> Suppose I have a function f(x,y) which does different operations for
> different types of arguments. How can I parse the arguments of f(x,y)
> and decide what properties x and y have?
>
> For instance, the function f(x,y) = x*y already does this, say for x, y
> real numbers or matrices.
>
> How can I do this for other types of arguments?
>
> For instance, consider real closed intervals [a,b] denoted by Interval(a,b).
>
> Then, the usual definition of the multiplication is
> Interval(a,b)*Interval(c,d) = Interval(min(ac,ad,bc,bd),max(ac,ad,bc,bd))
>
> Suppose f(x,y) = x*y
> Then, I would like to have '*' defined so that
> if x, y are real numbers, then f(x,y) = x*y is the usual product,
> but if x=Interval(a,b) and y=Interval(c,d), then
> f(Interval(a,b),Interval(c,d)) =
> Interval(min(ac,ad,bc,bd),max(ac,ad,bc,bd))
>
> Is there a simple way this can be done?
>
> TIA for any suggestions.
>
> -sen
>
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