#/***********************************************************
#    fibonacc.rb -- Fibonacci (フィボナッチ) 探索
#***********************************************************/

def fibonacci( a,  b, tolerance, f )
    if (a > b);  t = a;  a = b;  b = t;  end
    ia = (b - a) / tolerance
    ic = 1;  id = 2;  ib = 3
    while (ib < ia);  ic = id;  id = ib;  ib = ic + id;  end
    ia = 0;  tolerance = (b - a) / ib.to_f
    fc = f.call(a + ic * tolerance);  fd = f.call(a + id * tolerance)
    while (true) 
        if (fc > fd) 
            ia = ic;  ic = id;  id = ib - (ic - ia)
            if (ic == id); return a + id * tolerance; end
            fc = fd;  fd = f.call(a + id * tolerance)
        else 
            ib = id;  id = ic;  ic = ia + (ib - id)
            if (ic == id); return a + ic * tolerance; end
            fd = fc;  fc = f.call(a + ic * tolerance)
        end
    end
end

$count = 0
$xmin = 0.314

func = Proc.new do |x|
    value = (x - $xmin) * (x - $xmin)
    $count += 1
    printf("%4d:  f(%g) = %g\n", $count, x, value)
    value
end

printf("x = %g\n", fibonacci(0, 1, 1e-6, func))
exit 0