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I have 'if statements' from two different sources, which try to implement the same condition possibly in a different way. The 'if statements' are C. If at all possible I need a python script that can decide whether pairs of conditions are equivalent or not. A basic example:
source1: ((op1 != v1) || ((op2 != v2) || (op3 != v3)))
source2: ((op2 != v2) || (op1 != v1) || (op3 != v3))
Of course any operator is allowed, function calls and of course parentheses.
Any ideas are welcome.
Edit 1: The function calls have no side effects.
543
It is always legal in C programming to nest if-else statements, which means you can use one if or else if statement inside another if or else if statement(s).
if statement in C/C++ if statement is the most simple decision-making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e if a certain condition is true then a block of statement is executed otherwise not.
Use two if statements if both if statement conditions could be true at the same time. In this example, both conditions can be true. You can pass and do great at the same time. Use an if/else statement if the two conditions are mutually exclusive meaning if one condition is true the other condition must be false.
C has the following conditional statements: Use if to specify a block of code to be executed, if a specified condition is true. Use else to specify a block of code to be executed, if the same condition is false. Use else if to specify a new condition to test, if the first condition is false.
Here's the thing, the problem may (or may not) be NP-complete but unless this is within the inner-loop of something important (and the number of variable are small), build the entire truth table! It's extremely easy to do. It obviously grows as 2^n, but for small n this is completely feasible. Like the comments suggest, I'm assuming that the function calls have no side effects and simply output True or False.
I've posted a mockup example that solves your stated problem, adapt as needed. I rely on pythons parser to handle the evaluation of the expression.
import pyparsing as pypar
import itertools
def python_equiv(s):
return s.replace('||',' or ').replace('&&',' and ')
def substitute(s,truth_table, VARS):
for v,t in zip(VARS,truth_table):
s = s.replace(v,t)
return s
def check_statements(A1,A2):
VARS = set()
maths = pypar.oneOf("( ! = | & )")
keywords = pypar.oneOf("and or")
variable = pypar.Word(pypar.alphanums)
variable.setParseAction(lambda x: VARS.add(x[0]))
grammar = pypar.OneOrMore(maths | keywords | variable)
# Determine the variable names
grammar.parseString(A1)
grammar.parseString(A2)
A1 = python_equiv(A1)
A2 = python_equiv(A2)
bool_vals = map(str, [False,True])
for table in itertools.product(bool_vals,repeat=len(VARS)):
T1 = substitute(A1,table,VARS)
T2 = substitute(A2,table,VARS)
if eval(T1) != eval(T2):
print "FAIL AT ", table,
return False
print "Statements equiv:",
return True
# Original example
A1 = '''((op1 != v1) || ((op2 != v2) || (op3 != v3)))'''
A2 = '''((op2 != v2) || (op1 != v1) || (op3 != v3))'''
print check_statements(A1,A2)
# Example with a failure
A1 = '''((op1 != v1) || ((op2 != v2) || (op3 != v3)))'''
A2 = '''((op2 != v2) || (op1 != v1) && (op3 != v3))'''
print check_statements(A1,A2)
Gives as output:
Statements equiv: True
FAIL AT ('False', 'False', 'False', 'False', 'False', 'True') False
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