bound.py

from __future__ import division


class BoundedFloat(float):
    def __new__(self, value, minimum, maximum):
        return float.__new__(self, value)
        
    def __init__(self, value, minimum, maximum):
        if not (minimum <= value <= maximum):
            raise ValueError("Minimum must be less than or equal to value which"
                             " must be less than or equal to maximum.")
        float.__init__(value)
        self.minimum = minimum
        self.maximum = maximum

    def limit(self, new):
        if new < self.minimum:
            result = BoundedFloat(self.minimum, self.minimum, self.maximum)
        elif new > self.maximum:
            result = BoundedFloat(self.maximum, self.minimum, self.maximum)
        else:
            result = BoundedFloat(new, self.minimum, self.maximum)
        return result

    def __iadd__(self, other):
        new = self + other
        return self.limit(new)

    def __isub__(self, other):
        new = self - other
        return self.limit(new)
        
    def __imul__(self, other):
        new = self * other
        return self.limit(new)  

    def __itruediv__(self, other):
        new = self / other
        return self.limit(new)

    def __ifloordiv__(self, other):
        new = self // other
        return self.limit(new)