Question

I keep getting that error. Here’s the code (it’s for GCD):

Euc := proc (a, b) 
if b = 0 then a;
else c := b; 
d := a mod b;
b := d; a := c;
end if;
end proc;

I never use Maple because it gives me a headache and the documentation is a nightmare, but this assignment has to be done all in Maple… if I’m having trouble with simple GCD, I don’t see me writing RSA and El Gamal by Wednesday :s

edit: Fixed it with

Euc := proc (a, b) 
if b = 0 then a;
else c := b; 
d := a mod b;
Euc(c,d);
end if;
end proc;

But any I’d still like to know what the problem was, in case I have to do something similar again.

Answer 1

Your first version attempted to assign to the formal parameters of the procedure. That was the problem.

Suppose you call your original Euc and pass in 12 for parameter a and 8 for parameter b. Inside the body of Euc, as it runs in this instance, a evaluates to 12 and a does not evaluate to a name to which you can make an assignment. When you try and make an assignment to a or b inside Euc then you see that error.