Extending assignment Was: Functions with any number of arguments

On Sun, 15 Jan 2012, Aleksas Domarkas wrote:
> How  in Maxima define functions with any number of arguments ?
>
> For example, i need function MIN(arg1,arg2, ...)
> MIN(2) => 2
> MIN(3,4) =>3
> MIN(2/3,1/2,sqrt(2)/2) => 1/2

 MIN([args]) := block([m:first(args)],
                      for i in rest(args) do m:min(m,i),
                      m);

> Other example. How define G with following properties:
> G(n) => gamma(n)
> G(5) => 24
> G(a, x) => gamma_incomplete (a, x)
> G(a, z1, z2) =>  gamma_incomplete_generalized (a, z1, z2)

Use "length(args)" and "if <cond_1> then <expr_1> elseif ..."


What I wonder, is whether there is a more efficient way to check that
a list has empty tail than evaluate its length: I guess "empty" should
be a built-in function:

 empty(l) := block([simp:false], ?null(?cdr(l)));
 list_min(l) := block([f:first(l),r:rest(l)],
   if empty(r) then f else min(f, list_min(r)));
 MIN([args]) := list_min(args);

It would also be nice if "[a,b]:[1]" were not an error but instead
assigns false (NIL) to b. This would allow to do

 [a,b,c]:args;
 if c then /* 3 args */
 elseif b then /* 2 args */
 else ...

-- 
Regards,
ASK