RosettaCodeData/Task/Fibonacci-sequence/Bc/fibonacci-sequence.bc

#! /usr/bin/bc -q

define fib(x) {
    if (x <= 0) return 0;
    if (x == 1) return 1;

    a = 0;
    b = 1;
    for (i = 1; i < x; i++) {
        c = a+b; a = b; b = c;
    }
    return c;
}
fib(1000)
quit