% Functional Recursion: ;
fact IS RECUR [ 0 =, 1 first, pass, product, -1 +] % from wikipedia; 
 
% Product of a range: ; 
fact IS * count;

% Plain recursion: ;
fact IS OPERATION x {
  if x = 0 then 1 else x * fact (x - 1) endif
  };

% While loop: ;
fact IS OPERATION x {
prod := 1;
  WHILE x > 0 DO
      prod := prod * x;
      x := x - 1;
  ENDWHILE;
  prod
}

     % A basic divide by zero error: ;
     1 / 0
# OUTPUT:
?div

     % Errors are also values called faults, giving you their location: ;
     5 / 5 10 0 8
# OUTPUT:
1. 0.5 ?div 0.625

     % You can also define custom faults using 'fault': ;
     fault 'this is an error'
# OUTPUT:
this is an error