> fun mag a = if a < 0.0 then ~a
              else a;

val mag = fn : real -> real


> fun bi f a b T = let val c = (a + b)/2.0
           in if (mag (a - b)) < T then c
           else if (f c)*(f b) < 0.0 then (bi f c b T)
           else if (f c)*(f b) > 0.0 then (bi f a c T)
           else c end;

val bi = fn : (real -> real) -> real -> real -> real -> real


> fun poly x = x*x - 2.0;

val poly = fn : real -> real


> bi poly 1.0 2.0 0.00001;