operators.py

   1 # For licensing info see the included LICENSE file
   2 #
   3 # Josef Moudrik, <J dot Moudrik at standard google mail ending>, 2012
   4
   5 from math import sqrt
   6
   7 import number
   8 from exc import IncompatibleUnits
   9
  10
  11
  12 OPERATORS_ALL=[]
  13
  14 OP_CLASSES=[]
  15 OPERATORS_ARITHMETIC=[]
  16
  17 def register_operator(cl):
  18     OP_CLASSES.append(cl)
  19     return cl
  20
  21 class GenericOp(object):
  22     def __init__(self, arity, commutativity, name):
  23         self.arity = arity
  24         self.commutativity = commutativity
  25         self.name = name
  26
  27     def __call__(self, args):
  28         assert len(args) == self.getArity()
  29         values = map(lambda n: n.getValue(), args)
  30         sdsqs = map(lambda n: n.getSdSquare(), args)
  31         units = map(lambda n: n.getUnits(), args)
  32
  33         new_value, new_sdsq, new_units = self.computeNewNumber(values, sdsqs, units)
  34         return number.Number(new_value, sdsq=new_sdsq, string=self.name, units=new_units, parents=args)
  35
  36     def computeNewNumber(self, values, sdsqs, units):
  37         raise NotImplementedError
  38
  39     def getArity(self):
  40         return self.arity
  41
  42     def isCommutative(self):
  43         return self.commutativity
  44 #
  45 #
  46 #   Arithmetic Operators
  47 #
  48
  49 @register_operator
  50 class Plus(GenericOp):
  51     def __init__(self):
  52         super(Plus, self).__init__(2, True, "Plus")
  53
  54     def computeNewNumber(self, (n1v, n2v), (n1sdsq, n2sdsq), (u1, u2)):
  55         if u1 != u2:
  56             raise IncompatibleUnits
  57         new_value = n1v + n2v
  58         new_sdsq = n1sdsq + n2sdsq
  59         return new_value, new_sdsq, u1
  60
  61 @register_operator
  62 class Minus(GenericOp):
  63     def __init__(self):
  64         super(Minus, self).__init__(2, False, "Minus")
  65
  66     def computeNewNumber(self, (n1v, n2v), (n1sdsq, n2sdsq), (u1, u2)):
  67         if u1 != u2:
  68             raise IncompatibleUnits
  69         new_value = n1v - n2v
  70         new_sdsq = n1sdsq + n2sdsq
  71         return new_value, new_sdsq, u1
  72
  73 @register_operator
  74 class Mult(GenericOp):
  75     def __init__(self):
  76         super(Mult, self).__init__(2, True, "Mult")
  77
  78     def computeNewNumber(self, (n1v, n2v), (n1sdsq, n2sdsq), (u1, u2)):
  79         new_value = n1v * n2v
  80         new_sdsq = n1v**2 * n2sdsq + n2v**2 * n1sdsq
  81         return new_value, new_sdsq, number.units_join(u1, u2)
  82
  83 @register_operator
  84 class Div(GenericOp):
  85     def __init__(self):
  86         super(Div, self).__init__(2, False, "Div")
  87
  88     def computeNewNumber(self, (n1v, n2v), (n1sdsq, n2sdsq), (u1, u2)):
  89         new_value = n1v / n2v
  90         new_sdsq = n2v**(-2) * n1sdsq + n1v**2 * n2v**(-4) * n2sdsq
  91         return new_value, new_sdsq, number.units_diff(u1, u2)
  92
  93 #
  94 #       Numeric operators
  95 #
  96 # e.g. op(number) -> 2 * number
  97 #
  98
  99 class Times(GenericOp):
 100     def __init__(self, num):
 101         super(Times, self).__init__(1, True, str(num))
 102         self.num=num
 103
 104     def computeNewNumber(self, (n1v,), (n1sdsq, ), (u1,)):
 105         new_value = self.num * n1v
 106         new_sdsq = self.num**2 * n1sdsq
 107         return new_value, new_sdsq, u1
 108
 109 #
 110 #       Unit Conversions
 111 #
 112
 113 # TODO TODO TODO
 114
 115 #
 116 #   All together
 117 #
 118
 119 OPERATORS_ARITHMETIC = map(lambda x: x() , OP_CLASSES)
 120