Changed function name.

src/rules/integrals.py

-from .utils import find_variables, replace_variable, find_variable
+from .utils import find_variables, substitute, find_variable
 from ..node import ExpressionLeaf as L, OP_INT, OP_INT_INDEF, OP_MUL, OP_DIV, \
         OP_LOG, OP_SIN, OP_COS, Scope, sin, cos, ln, integral, indef, absolute
 from ..possibilities import Possibility as P, MESSAGES
@@ -40,7 +40,7 @@ def solve_integral(integral, F):
     x, lbnd, ubnd = integral[1:4]
 
     if x != find_variable(F):
-        return replace_variable(F, x, ubnd) - replace_variable(F, x, lbnd)
+        return substitute(F, x, ubnd) - substitute(F, x, lbnd)
 
     return indef(F, lbnd, ubnd)
 
@@ -61,7 +61,7 @@ def solve_indef(root, args):
     Fx, a, b = root
     x = find_variable(Fx)
 
-    return replace_variable(Fx, x, b) - replace_variable(Fx, x, a)
+    return substitute(Fx, x, b) - substitute(Fx, x, a)
 
 
 def match_integrate_variable_power(node):

src/rules/utils.py

@@ -111,7 +111,7 @@ def find_variable(exp):
     return L(first_sorted_variable(variables))
 
 
-def replace_variable(f, x, replacement):
+def substitute(f, x, replacement):
     """
     Replace all occurences of variable x in function f with the specified
     replacement.
@@ -122,6 +122,6 @@ def replace_variable(f, x, replacement):
     if f.is_leaf:
         return f
 
-    children = map(lambda c: replace_variable(c, x, replacement), f)
+    children = map(lambda c: substitute(c, x, replacement), f)
 
     return N(f.op, *children)

tests/test_rules_utils.py

 from src.rules import utils
 from src.rules.utils import least_common_multiple, is_fraction, partition, \
-        find_variables, first_sorted_variable, find_variable, replace_variable
+        find_variables, first_sorted_variable, find_variable, substitute
 from tests.rulestestcase import tree, RulesTestCase
 
 
@@ -50,10 +50,10 @@ class TestRulesUtils(RulesTestCase):
         self.assertEqual(find_variable(tree('1 + 2')), x)
         self.assertEqual(find_variable(tree('y ^ 2')), y)
 
-    def test_replace_variable(self):
+    def test_substitute(self):
         x, a = tree('x, a')
 
-        self.assertEqual(replace_variable(x, x, a), a)
-        self.assertEqual(replace_variable(tree('x2'), x, a), tree('a2'))
-        self.assertEqual(replace_variable(tree('y + x + 1'), x, a),
+        self.assertEqual(substitute(x, x, a), a)
+        self.assertEqual(substitute(tree('x2'), x, a), tree('a2'))
+        self.assertEqual(substitute(tree('y + x + 1'), x, a),
                          tree('y + a + 1'))