Matching mathematical expressions

We encounter mathematical operations all the time. Logic programming is a very efficient way of comparing expressions and finding out unknown values. Let's see how to do that.

Create a new Python file and import the following packages:

from logpy import run, var, fact 
import logpy.assoccomm as la 

Define a couple of mathematical operations:

# Define mathematical operations 
add = 'addition' 
mul = 'multiplication' 

Both addition and multiplication are commutative operations. Let's specify that:

# Declare that these operations are commutative 
# using the facts system 
fact(la.commutative, mul) 
fact(la.commutative, add) 
fact(la.associative, mul) 
fact(la.associative, add) 

Let's define some variables:

# Define some variables 
a, b, c = var('a'), var('b'), var('c') 

Consider the following expression:

expression_orig = 3 x (-2) + (1 + 2 x 3) x (-1) 

Let's generate this expression with masked variables. The first expression would be:

• expression1 = (1 + 2 x a) x...