Type control

[salvomic]

ok, I'm working about this code:

Code:


EXPORT Multinomd(n, k, p)
// Multinomial distribution (n>0,{list k_i}, {list p_i})
BEGIN

IF ((type(k) ≠ 6) OR (type(p) ≠ 6)) THEN 
return "2nd and 3th argument must be a list"; ELSE
n:= ip(n);
return  (n!/ΠLIST(k!))*ΠLIST(p^k);
END; // if 
END;

for now it' almost ok, but I must also control the number of parameters, to avoid the "error: Bad Argument value" if they are less or more than 3.
(in CAS version I could use "IF argc !=3 ...)

Other: why in CAS I could write
IF ((type(k) != DOM_LIST) OR (type(p) != DOM_LIST)) THEN

and in non-CAS it doesn't works?
I must use
IF ((type(k) ≠ 6) OR (type(p) ≠ 6)) THEN
instead?