(Prolog) Calculating the factorial

PREDICATES
  nondeterm factorial(integer, integer)
CLAUSES
 
  factorial(0,1).
  factorial(Number,Factorial) if
    Number > 0
    and LowerNumber = Number - 1
    and factorial(LowerNumber, X)
    and Factorial = Number * X.
GOAL
  factorial(5,X).

'factorial' links

• C++