digital_simulator/Expr.py

   1 #!/usr/bin/python
   2 # vim: set fileencoding=utf8
   3 # Created:20080216
   4 # By Jeff Connelly
   5 #
   6 # Trinary expression evaluator
   7
   8 from Symbols import *
   9 from Trits import Trits
  10
  11 DEBUG = False
  12
  13 unary_functions = {
  14         # Everyone agrees on
  15         u"/": Trits("10i"),
  16
  17         # Mouftah-based
  18         u"∇": Trits("1ii"), u"└": Trits("1ii"),
  19         u"∆": Trits("11i"), u"┘": Trits("11i"),
  20         u"¬": Trits("001"),
  21         u"⌐": Trits("i00"),
  22
  23         # Grubb-based
  24         u"↘": Trits("ii0"),
  25         u"↗": Trits("011"),
  26         u"∩": Trits("01i"),
  27         u"∪": Trits("10i"),
  28
  29         # Ternary-logic-minimization-literature-based
  30         u"♨": Trits("01i")
  31         }
  32
  33 def evaluate_unary(function, inputs):
  34     """Given a unary function number in a Trits object, f, pass
  35     all the trits in the inputs object through the function."""
  36
  37     assert isinstance(function, Trits), \
  38             "Need to pass a Trits object as function"
  39     assert isinstance(inputs, Trits), \
  40             "You must pass a Trits object in inputs"
  41
  42     outputs = []
  43     for t in inputs:
  44         outputs.append({
  45                 False: function[0],
  46                 None: function[1],
  47                 True: function[2]
  48                 }[t])
  49
  50     return Trits(outputs)
  51
  52 class Expr(object):
  53     def __init__(self, s):
  54         assert len(s) > 0, "Empty string can't evaluate"
  55
  56         variable = s[-1]
  57         assert variable.isalpha(), "Only accept expressions of form xxxxA, where x=unary operators, A=variable"
  58         if DEBUG: print "Variable:", variable
  59
  60         # Evaluate gates from right-to-left
  61         unary_gates = reversed(s[:-1])
  62
  63         # Start with identity function
  64         total_unary = Trits("i01")
  65
  66         # Evaluate with unary function on the identity
  67         for gate in unary_gates:
  68             if DEBUG: print "Gate:", gate.encode('utf8')
  69             total_unary = evaluate_unary(unary_functions[gate], total_unary)
  70
  71         # Now total_unary is the function# of all the unary gates
  72         self.total_unary = total_unary
  73
  74     def evaluate(self, inputs):
  75         return evaluate_unary(self.total_unary, inputs)
  76
  77 if __name__ == "__main__":
  78     s = u"⌐∇a"
  79     print "Expression:", s.encode('utf8')
  80     e = Expr(s)
  81     print "Total unary function is:", e.total_unary
  82     print
  83
  84     ins = Trits("iiiiiiiii00000001111111")
  85     print "Passing in trit vector as 'a':"
  86     print "a:\t", ins
  87     print s.encode('utf8') + ":\t", e.evaluate(ins)
  88