Fix inheritance order on IdentityMapper. Add test. (+)

Mapper: Variable is an AlgebraicLeaf.
Fix NonrecursiveIdentityMapper.

src/mapper/__init__.py

@@ -18,6 +18,9 @@ class Mapper(object):
         else:
             return self.map_foreign(expr, *args, **kwargs)
 
+    def map_variable(self, expr, *args, **kwargs):
+        return self.map_algebraic_leaf(self, expr, *args, **kwargs)
+
     def map_subscript(self, expr, *args, **kwargs):
         return self.map_algebraic_leaf(self, expr, *args, **kwargs)
 
@@ -161,9 +164,10 @@ class IdentityMapperBase(object):
 
 
 
-class IdentityMapper(RecursiveMapper, IdentityMapperBase):
+class IdentityMapper(IdentityMapperBase, RecursiveMapper):
     def handle_unsupported_expression(self, expr, *args, **kwargs):
         return expr
 
-class NonrecursiveIdentityMapper(Mapper, IdentityMapperBase):
-    pass
+class NonrecursiveIdentityMapper(IdentityMapperBase, Mapper):
+    def handle_unsupported_expression(self, expr, *args, **kwargs):
+        return expr

src/mapper/substitutor.py

@@ -5,23 +5,23 @@ import pymbolic.mapper
 
 class SubstitutionMapper(pymbolic.mapper.IdentityMapper):
     def __init__(self, variable_assignments):
-        self.Assignments = variable_assignments
+        self.assignments = variable_assignments
 
     def map_variable(self, expr):
         try:
-            return self.Assignments[expr]
+            return self.assignments[expr]
         except KeyError:
             return expr
 
     def map_subscript(self, expr):
         try:
-            return self.Assignments[expr]
+            return self.assignments[expr]
         except KeyError:
             return pymbolic.mapper.IdentityMapper.map_subscript(self, expr)
 
     def map_lookup(self, expr):
         try:
-            return self.Assignments[expr]
+            return self.assignments[expr]
         except KeyError:
             return pymbolic.mapper.IdentityMapper.map_lookup(self, expr)
 

test/test_pymbolic.py

@@ -9,8 +9,13 @@ class TestPymbolic(unittest.TestCase):
 
         x = var("x")
         u = (x+1)**5
-        print expand(u)
+        expand(u)
 
+    def test_substitute(self):
+        from pymbolic import parse, substitute, evaluate
+        u = parse("5+x.min**2")
+        xmin = parse("x.min")
+        assert evaluate(substitute(u, {xmin:25})) == 630
             
 if __name__ == '__main__':
     unittest.main()