edouble.py

from math import sqrt
class EDouble(object):
    def __init__(self, val, err):
        self.val = float(val)
        self.err = abs(float(err))

    def __mul__(self, other):
        if not isinstance(other, EDouble):
            other = EDouble(other, 0.0)

        rVal = self.val * other.val
        rel_rErr = sqrt((self.err / self.val)**2.0 + ( other.err / other.val )**2.0)
        return EDouble(rVal, rel_rErr * rVal)

    def __div__(self, other):
        if not isinstance(other, EDouble):
            other = EDouble(other, 0.0)

        rVal = self.val / other.val
        rel_rErr = sqrt((self.err / self.val)**2.0 + ( other.err / other.val )**2.0)
        return EDouble(rVal, rel_rErr * rVal)

    def __add__(self, other):
        if not isinstance(other, EDouble):
            other = EDouble(other, 0.0)

        rVal = self.val + other.val
        rErr = sqrt(self.err**2.0 + other.err**2.0)
        return EDouble(rVal, rErr)

    def __sub__(self, other):
        if not isinstance(other, EDouble):
            other = EDouble(other, 0.0)

        rVal = self.val - other.val
        rErr = sqrt(self.err**2.0 + other.err**2.0)
        return EDouble(rVal, rErr)

    def __repr__(self):
        return "${} \\pm {}$".format(self.val, self.err)




# somewhat optimized
# class EDouble(object):
#     def __init__(self, val, err):
#         self.val = float(val)
#         self.err = abs(float(err))

#     def __mul__(self, other):
#         if isinstance(other, EDouble):
#             rVal = self.val * other.val
#             rel_rErr = sqrt((self.err / self.val)**2.0 + ( other.err / other.val )**2.0)
#             return EDouble(rVal, rel_rErr * rVal)
#         else:
#             rVal = self.val * other
#             rel_rErr = (self.err / self.val)
#             return EDouble(rVal, rel_rErr * rVal)

#     def __div__(self, other):
#         if isinstance(other, EDouble):
#             rVal = self.val / other.val
#             rel_rErr = sqrt((self.err / self.val)**2.0 + ( other.err / other.val )**2.0)
#             return EDouble(rVal, rel_rErr * rVal)
#         else:
#             rVal = self.val / other
#             rel_rErr = self.err / self.val
#             return EDouble(rVal, rel_rErr * rVal)

#     def __add__(self, other):
#         if isinstance(other, EDouble):
#             rVal = self.val + other.val
#             rErr = sqrt(self.err**2.0 + other.err**2.0)
#             return EDouble(rVal, rErr)
#         else:
#             rVal = self.val + other
#             rErr = self.err
#             return EDouble(rVal, rErr)

#     def __sub__(self, other):
#         if isinstance(other, EDouble):
#             rVal = self.val - other.val
#             rErr = sqrt(self.err**2.0 + other.err**2.0)
#             return EDouble(rVal, rErr)
#         else:
#             rVal = self.val - other
#             rErr = self.err
#             return EDouble(rVal, rErr)

#     def __repr__(self):
#         return "${} \\pm {}$".format(self.val, self.err)