sidef/scripts/stern-brocot_sequence.sf

#!/usr/bin/ruby

# Declare a function to generate the Stern-Brocot sequence
func stern_brocot {
    var list = [1, 1];
    {
        list.append(list[0]+list[1], list[1]);
        list.shift;
    }
}

# Show the first fifteen members of the sequence.
1..15 -> map(stern_brocot()).join(' ').say;

# Show the (1-based) index of where the numbers 1-to-10 first appears
# in the sequence, and where the number 100 first appears in the sequence.
[(1..10)..., 100].each { |i|
    var index = 1;
    var generator = stern_brocot();
    while (generator() != i) {
        ++index;
    }
    say "First occurrence of #{i} is at index #{index}";
}

# Check that the greatest common divisor of all the two consecutive
# members of the series up to the 1000th member, is always one.
var generator = stern_brocot();
var (a, b) = (generator(), generator());
{
    assert_eq(Math.gcd(a, b), 1);
    a = b;
    b = generator();
} * 1000;

say "All GCD's are 1";