Add support for more operators

setup.py

@@ -24,7 +24,7 @@
     author_email='trey@treymorris.com',
     description='auto generate truth tables',
     long_description=open('README.rst').read(),
-    install_requires=['prettytable'],
+    install_requires=['prettytable', 'pyparsing'],
     classifiers=['Development Status :: 5 - Production/Stable',
                  'License :: OSI Approved :: Apache Software License'],
     keywords=['truth', 'table', 'truth table', 'truthtable', 'logic'],

truths/truths.py

@@ -18,50 +18,148 @@
 import itertools
 from prettytable import PrettyTable
 import re
+import pyparsing
 
+# dict of boolean operations
+operations = {
+    'not':      (lambda x:      not x),
+    '-':        (lambda x:      not x),
+    '~':        (lambda x:      not x),
 
-class Gob(object):
-    pass
+    'or':       (lambda x, y:   x or y),
+    'nor':      (lambda x, y:   not (x or y)),
+    'xor':      (lambda x, y:   x != y),
+
+    'and':      (lambda x, y:   x and y),
+    'nand':     (lambda x, y:   not (x and y)),
+    'xand':     (lambda x, y:   not (x and y)),
+
+    '=>':       (lambda x, y:   (not x) or y),
+    '->':       (lambda x, y:   (not x) or y),
+    'implies':  (lambda x, y:   (not x) or y),
+
+    '=':        (lambda x, y:   x == y),
+    '==':       (lambda x, y:   x == y),
+    '!=':       (lambda x, y:   x != y),
+}
+
+
+def recursive_map(func, data):
+    """Recursively applies a map function to a list and all sublists."""
+    if isinstance(data, list):
+        return [recursive_map(func, elem) for elem in data]
+    else:
+        return func(data)
+
+
+def string_to_bool(s):
+    """Converts a string to boolean if string is either 'True' or 'False'
+    otherwise returns it unchanged.
+    """
+    if s == 'True':
+        return True
+    elif s == 'False':
+        return False
+    return s
+
+
+def solve_phrase(p):
+    """Recursively evaluates a logical phrase that has been grouped into
+    sublists where each list is one operation.
+    """
+    if isinstance(p, bool):
+        return p
+    if isinstance(p, list):
+        # list with just a list in it
+        if len(p) == 1:
+            return solve_phrase(p[0])
+        # single operand operation
+        if len(p) == 2:
+            return operations[p[0]](solve_phrase(p[1]))
+        # double operand operation
+        else:
+            return operations[p[1]](solve_phrase(p[0]), solve_phrase([p[2]]))
+
+
+def group_operations(p):
+    """Recursively groups logical operations into seperate lists based on
+    the order of operations such that each list is one operation.
+
+    Order of operations is:
+        not, and, or, implication
+    """
+    if isinstance(p, list):
+        if len(p) == 1:
+            return p
+        for x in ['not', '~', '-']:
+            while x in p:
+                index = p.index(x)
+                p[index] = [x, group_operations(p[index+1])]
+                p.pop(index+1)
+        for x in ['and', 'nand', 'xand']:
+            while x in p:
+                index = p.index(x)
+                p[index] = [group_operations(p[index-1]), x, group_operations(p[index+1])]
+                p.pop(index+1)
+                p.pop(index-1)
+        for x in ['or', 'nor', 'xor']:
+            while x in p:
+                index = p.index(x)
+                p[index] = [group_operations(p[index-1]), x, group_operations(p[index+1])]
+                p.pop(index+1)
+                p.pop(index-1)
+    return p
 
 
 class Truths(object):
-    def __init__(self, base=None, phrases=None, ints=True):
-        if not base:
+    def __init__(self, bases=None, phrases=None, ints=True):
+        if not bases:
             raise Exception('Base items are required')
-        self.base = base
+        self.bases = bases
         self.phrases = phrases or []
         self.ints = ints
 
         # generate the sets of booleans for the bases
         self.base_conditions = list(itertools.product([False, True],
-                                                      repeat=len(base)))
+                                                      repeat=len(bases)))
 
         # regex to match whole words defined in self.bases
         # used to add object context to variables in self.phrases
-        self.p = re.compile(r'(?<!\w)(' + '|'.join(self.base) + ')(?!\w)')
+        self.p = re.compile(r'(?<!\w)(' + '|'.join(self.bases) + ')(?!\w)')
+
+        # uesd for parsing logical operations and parenthesis
+        self.to_match = pyparsing.Word(pyparsing.alphanums)
+        for item in itertools.chain(self.bases, [key for key, val in operations.items()]):
+            self.to_match |= item
+        self.parens = pyparsing.nestedExpr( '(', ')', content=self.to_match)
 
     def calculate(self, *args):
-        # store bases in an object context
-        g = Gob()
-        for a, b in zip(self.base, args):
-            setattr(g, a, b)
+        bools = dict(zip(self.bases, args))
 
-        # add object context to any base variables in self.phrases
-        # then evaluate each
         eval_phrases = []
-        for item in self.phrases:
-            item = self.p.sub(r'g.\1', item)
-            eval_phrases.append(eval(item))
+        for phrase in self.phrases:
+            # substitute bases in phrase with boolean values as strings
+            phrase = self.p.sub(lambda match: str(bools[match.group(0)]), phrase)
+            # wrap phrase in parens
+            phrase = '(' + phrase + ')'
+            # parse the expression using pyparsing
+            interpreted = self.parens.parseString(phrase).asList()[0]
+            # convert any 'True' or 'False' to boolean values
+            interpreted = recursive_map(string_to_bool, interpreted)
+            # group operations
+            interpreted = group_operations(interpreted)
+            # evaluate the phrase
+            eval_phrases.append(solve_phrase(interpreted))
 
         # add the bases and evaluated phrases to create a single row
-        row = [getattr(g, b) for b in self.base] + eval_phrases
+        row = [val for key, val in bools.items()] + eval_phrases
         if self.ints:
             return [int(c) for c in row]
         else:
             return row
 
     def __str__(self):
-        t = PrettyTable(self.base + self.phrases)
+        t = PrettyTable(self.bases + self.phrases)
         for conditions_set in self.base_conditions:
             t.add_row(self.calculate(*conditions_set))
         return str(t)