--- a/python/c3/astnodes.py	Fri Jul 12 17:42:39 2013 +0200
+++ b/python/c3/astnodes.py	Sat Jul 13 11:12:24 2013 +0200
@@ -32,10 +32,11 @@
 types must be comparable.
 
 There are the following types:
-- base type
-- struct type
-- pointer type
-- typedef type
+- base type -> basic type (built in)
+- struct type -> a composite type that contains a list of named fields 
+            of other types
+- pointer type -> a type that points to some other type
+- typedef type -> a named type indicating another type
 - function type
 """
 
@@ -190,84 +191,89 @@
         return 'BINOP {}'.format(self.op)
 
 class VariableUse(Expression):
-   def __init__(self, target, loc):
-      self.target = target
-      self.loc = loc
-   def __repr__(self):
-      nm = self.target.name if hasattr(self.target, 'name') else ''
-      return 'VAR USE {}'.format(nm)
+    def __init__(self, target, loc):
+        self.target = target
+        self.loc = loc
+    def __repr__(self):
+        nm = self.target
+        return 'VAR USE {}'.format(nm)
 
 class Literal(Expression):
-   def __init__(self, val, loc):
-      self.val = val
-      self.loc = loc
-   def __repr__(self):
-      return 'LITERAL {}'.format(self.val)
+    def __init__(self, val, loc):
+        self.val = val
+        self.loc = loc
+    def __repr__(self):
+        return 'LITERAL {}'.format(self.val)
 
 class FunctionCall(Expression):
-  def __init__(self, proc, args, loc):
-    self.proc = proc
-    self.args = args
-    self.loc = loc
-  def __repr__(self):
-    return 'CALL {0} '.format(self.proc)
+    def __init__(self, proc, args, loc):
+        self.proc = proc
+        self.args = args
+        self.loc = loc
+    def __repr__(self):
+        return 'CALL {0} '.format(self.proc)
 
 # Statements
 class Statement(Node):
-    pass
+    def __init__(self, loc):
+        self.loc = loc
+
 
 class CompoundStatement(Statement):
     def __init__(self, statements):
         self.statements = statements
+        for s in self.statements:
+            assert isinstance(s, Statement)
 
     def __repr__(self):
         return 'COMPOUND STATEMENT'
 
-class EmptyStatement(Statement):
-   def __repr__(self):
-      return 'NOP'
 
 class ReturnStatement(Statement):
-   def __init__(self, expr, loc):
-      self.expr = expr
-      self.loc = loc
-   def __repr__(self):
-      return 'RETURN STATEMENT'
+    def __init__(self, expr, loc):
+        super().__init__(loc)
+        self.expr = expr
+
+    def __repr__(self):
+        return 'RETURN STATEMENT'
 
 class Assignment(Statement):
     def __init__(self, lval, rval, loc):
+        super().__init__(loc)
         assert isinstance(lval, Node)
         assert isinstance(rval, Node)
-        assert isinstance(loc, SourceLocation)
         self.lval = lval
         self.rval = rval
-        self.loc = loc
 
     def __repr__(self):
         return 'ASSIGNMENT'
 
 class ExpressionStatement(Statement):
     def __init__(self, ex, loc):
+        super().__init__(loc)
         self.ex = ex
-        self.loc = loc
-        assert isinstance(loc, SourceLocation)
+
     def __repr__(self):
         return 'Epression'
 
+
 class IfStatement(Statement):
-   def __init__(self, condition, truestatement, falsestatement, loc):
-      self.condition = condition
-      self.truestatement = truestatement
-      self.falsestatement = falsestatement
-      self.loc = loc
-   def __repr__(self):
-      return 'IF-statement'
+    def __init__(self, condition, truestatement, falsestatement, loc):
+        super().__init__(loc)
+        self.condition = condition
+        self.truestatement = truestatement
+        self.falsestatement = falsestatement
+
+    def __repr__(self):
+        return 'IF-statement'
+
 
 class WhileStatement(Statement):
-   def __init__(self, condition, statement, loc):
-      self.condition = condition
-      self.statement = statement
-      self.loc = loc
-   def __repr__(self):
-      return 'WHILE-statement'
+    def __init__(self, condition, statement, loc):
+        super().__init__(loc)
+        self.condition = condition
+        self.statement = statement
 
+    def __repr__(self):
+        return 'WHILE-statement'
+