diff --git a/translator.py b/translator.py
index ac7338f..a857fc5 100644
--- a/translator.py
+++ b/translator.py
@@ -8,7 +8,12 @@ def translate(func):
     source = inspect.getsource(func)
     lines = list(source.splitlines())
 
-     # skip first two lines
+    # skip first two lines
+    # assume they are
+    #     @translate
+    #     def blahblah():
+    assert lines[0].lstrip().startswith('@')
+    assert lines[1].lstrip().startswith('def')
     first_line_len = len(lines[2])
     indent = first_line_len - len(lines[2].lstrip())
     source = '\n'.join(line[indent:] for line in lines[2:])
@@ -38,10 +43,18 @@ with self.ifelse(__CONDITION__) as _ifelse_:
 _return_template = 'self.ret(__RETURN__)'
 
 def load_template(string):
+    '''
+    Since ast.parse() returns a ast.Module node,
+    it is more useful to trim the Module and get to the first item of body
+    '''
     tree = ast.parse(string)  # return a Module
     return tree.body[0]       # get the first item of body
 
 class ExpandControlFlow(ast.NodeTransformer):
+    '''
+    Expand control flow contructs.
+    These are the most tedious thing to do in llvm_cbuilder.
+    '''
     def visit_If(self, node):
         condition = node.test
         mapping = {
@@ -51,22 +64,29 @@ class ExpandControlFlow(ast.NodeTransformer):
         }
 
         ifelse = load_template(_if_else_template)
-        ifelse = NameReplacer(mapping).visit(ifelse)
+        ifelse = MacroExpander(mapping).visit(ifelse)
         newnode = ast.copy_location(ifelse, node)
         return self.generic_visit(newnode)
 
     def visit_Return(self, node):
         mapping = {'__RETURN__' : node.value}
         ret = load_template(_return_template)
-        repl = NameReplacer(mapping).visit(ret)
+        repl = MacroExpander(mapping).visit(ret)
         return ast.copy_location(repl, node)
 
-class NameReplacer(ast.NodeTransformer):
+class MacroExpander(ast.NodeTransformer):
     def __init__(self, mapping):
         self.mapping = mapping
 
     def visit_With(self, node):
-        if (len(node.body)==1
+        '''
+        Expand X in the following:
+            with blah:
+                X
+        Nothing should go before or after X.
+        X must be a list of nodes.
+        '''
+        if (len(node.body)==1 # the body of
           and isinstance(node.body[0], ast.Expr)
           and isinstance(node.body[0].value, ast.Name)):
             try:
@@ -76,9 +96,12 @@ class NameReplacer(ast.NodeTransformer):
             else:
                 old = node.body[0]
                 node.body = repl
-        return self.generic_visit(node)
+        return self.generic_visit(node) # recursively apply expand all macros
 
     def visit_Name(self, node):
+        '''
+        Expand all Name node to simple value
+        '''
         if type(node.ctx) is ast.Load:
             try:
                 repl = self.mapping.pop(node.id)