/*  File: fibonacci.P
/*  Author: Ned Okie (et al.)
/*  Date:   9/15/95
/*  Purpose: To illustrate basic xsb rules and syntax
/*  To invoke prolog compiler: /software/unix/XSB/emu/xsb -i
*/

fib(0,1).     /* Base case 1 */
fib(1,1).     /* Base case 2   (Note that 2 base cases are needed) */

fib(M,N) :- M>1, M1  is M - 1, M2 is M - 2,     /* Recursive definition */
                 fib(M1,N1), fib(M2,N2),
                 N is N1 + N2.

fibdemo1(X)  :- fib(X,N), write(N).            /* Demonstrations */
fibdemo2     :- read(X), fib(X,N), write(N).