ifactors Test Problem

[toml_12953]

I'm trying to create an is_prime function:

Code:

EXPORT is_prime(X)
begin
  if dim(ifactors(X))=={2} then
    return true;
  else
    return false;
  end;
end;

dim(ifactors(7))

returns {2} but when I call is_prime(7), I get Error: Bad argument type.

I tried with both upper and lowercase X and I tried the 2 both in and out of braces.

What am I doing wrong?