Moved factors rewrite rules to separate file.

src/rules/__init__.py

 from ..node import OP_ADD, OP_MUL, OP_DIV, OP_POW
-from .poly import match_combine_polynomes, match_expand
+from .poly import match_combine_polynomes
+from .factors import match_expand
 from .powers import match_add_exponents, match_subtract_exponents, \
         match_multiply_exponents, match_duplicate_exponent, \
         match_remove_negative_exponent, match_exponent_to_root

src/rules/factors.py

+from ..node import OP_ADD, OP_MUL
+from ..possibilities import Possibility as P, MESSAGES
+from .utils import nary_node
+
+
+def match_expand(node):
+    """
+    a * (b + c) -> ab + ac
+    """
+    assert node.is_op(OP_MUL)
+
+    # TODO: fix!
+    return []
+
+    p = []
+    a = []
+    bc = []
+
+    for n in node.get_scope():
+        if n.is_leaf():
+            a.append(n)
+        elif n.op == OP_ADD:
+            bc.append(n)
+
+    if a and bc:
+        for a_node in a:
+            for bc_node in bc:
+                p.append(P(node, expand_single, a_node, bc_node))
+
+    return p
+
+
+def expand_single(root, args):
+    """
+    Combine a leaf (a) multiplied with an addition of two expressions
+    (b + c) to an addition of two multiplications.
+
+    >>> a * (b + c) -> a * b + a * c
+    """
+    a, bc = args
+    b, c = bc
+    scope = root.get_scope()
+
+    # Replace 'a' with the new expression
+    scope[scope.index(a)] = a * b + a * c
+
+    # Remove the old addition
+    scope.remove(bc)
+
+    return nary_node('*', scope)

src/rules/poly.py

 from itertools import combinations
 
-from ..node import ExpressionNode as Node, OP_ADD, OP_MUL
+from ..node import OP_ADD
 from ..possibilities import Possibility as P, MESSAGES
 from .utils import nary_node
 from .numerics import add_numerics
 
 
-def match_expand(node):
-    """
-    a * (b + c) -> ab + ac
-    """
-    assert node.is_op(OP_MUL)
-
-    # TODO: fix!
-    return []
-
-    p = []
-    a = []
-    bc = []
-
-    for n in node.get_scope():
-        if n.is_leaf():
-            a.append(n)
-        elif n.op == OP_ADD:
-            bc.append(n)
-
-    if a and bc:
-        for a_node in a:
-            for bc_node in bc:
-                p.append(P(node, expand_single, a_node, bc_node))
-
-    return p
-
-
-def expand_single(root, args):
-    """
-    Combine a leaf (a) multiplied with an addition of two expressions
-    (b + c) to an addition of two multiplications.
-
-    >>> a * (b + c) -> a * b + a * c
-    """
-    a, bc = args
-    b, c = bc
-    scope = root.get_scope()
-
-    # Replace 'a' with the new expression
-    scope[scope.index(a)] = Node('+', Node('*', a, b), \
-                                      Node('*', a, c))
-
-    # Remove the old addition
-    scope.remove(bc)
-
-    return nary_node('*', scope)
-
-
 def match_combine_polynomes(node, verbose=False):
     """
     n + exp + m -> exp + (n + m)

tests/test_rules_factors.py

+from src.rules.factors import match_expand, expand_single
+from src.possibilities import Possibility as P
+from tests.rulestestcase import RulesTestCase
+from tests.test_rules_poly import tree
+
+
+class TestRulesFactors(RulesTestCase):
+
+    def test_match_expand(self):
+        pass
+
+    def test_expand_single(self):
+        pass