diff --git a/code/code_gen/code_gen.py b/code/code_gen/code_gen.py
index d30add2..9d8953a 100644
--- a/code/code_gen/code_gen.py
+++ b/code/code_gen/code_gen.py
@@ -4,6 +4,8 @@
 
 from lark import Lark, Visitor, Transformer, v_args, Token
 
+from post import *
+
 
 try:
     input = raw_input   # For Python2 compatibility
@@ -259,7 +261,7 @@ class CalculateTree(Transformer):
 
         return ""
 
-    def assign_var(self, *args): # name, (value, dep)):
+    def assign_var(self, *args):
 
         vname, vdef = args
         self.definitions[vname.value] = vdef
@@ -278,7 +280,7 @@ class CalculateTree(Transformer):
 
         return ""
 
-    def assign_avg_var(self, *args): # weight, *args): #name, (value, dep)):
+    def assign_avg_var(self, *args):
 
         weight = args[0]
         vlist = args[1:]
@@ -375,6 +377,16 @@ class FortranProgram:
 
         tree = self.tree_parser.parse(terms_input)
 
+        print "< IR 1 >"
+        ir1 = Stage1(tree)
+        print ir1
+
+        print "< IR 2 >"
+        ir2 = Stage2(ir1)
+        print ir2
+
+
+
         self.parser.transform(tree)
 
 
@@ -617,7 +629,7 @@ def test():
     fp = FortranProgram(terms_raw)
 
 
-    print mod_form.format( fp.print_program() )
+    # print mod_form.format( fp.print_program() )
 
     # fp.print_graph()
 
diff --git a/code/code_gen/post.py b/code/code_gen/post.py
new file mode 100644
index 0000000..e96002b
--- /dev/null
+++ b/code/code_gen/post.py
@@ -0,0 +1,149 @@
+from lark import Lark, Visitor, Transformer, v_args, Token
+
+
+class ExpInspector(Visitor):
+    def __init__(self):
+        self.fluctuation = False
+        self.dep = set([])
+        self.deriv = set([])
+
+    @classmethod
+    def inspect(cls, tree):
+        self = cls()
+        return self(tree)
+
+    def __call__(self, tree):
+        self.visit(tree)
+        return self.fluctuation, self.dep, self.deriv
+
+    def fluc(self, tree):
+        self.fluctuation = True
+
+    def var(self, tree):
+        self.dep.add(tree.children[0].value)
+
+    def dnx (self, tree):
+        op, v = tree.children
+        deriv = "{}_{}".format(op.data, v.value)
+        self.dep.add(deriv)
+        self.deriv.add((op.data, v.value))
+
+
+class FieldBase (object):
+    def __init__ (self, name, fdict):
+        self.name = name
+        self.array = name
+        self.dep = set([])
+        self.fluc = False
+        self.fdict = fdict
+
+    def depends_on (self, a):
+        return (a in self.dep)
+
+    def __repr__ (self):
+        return self.name
+
+
+class Field (FieldBase):
+
+    def __init__ (self, name, exp, fdict):
+        super(Field,self).__init__(name, fdict)
+        self.exp = exp
+        self.fluc, self.dep, self.derivs = ExpInspector.inspect(exp)
+
+        '''
+        for a in self.dep:
+            if a not in self.fdict:
+                raise StandardError(a + " is not defined")
+        '''
+
+    def is_fluctuation (self):
+        return self.fluc
+
+    def code (self, alloc):
+        transform(self.exp)
+        return (a in self.dep)
+
+
+class DerivedField (FieldBase):
+
+    def __init__ (self, op, v, fdict):
+        name = "{}_{}".format(op, v)
+        super(DerivedField,self).__init__(name, fdict)
+        self.op = op
+        self.v = v
+        self.dep = set([v])
+
+    def code (self):
+        return "call {0} ( {2}, {1} )".format(self.op, self.v, self.array)
+
+class CollectDefinitions(Visitor):
+
+    def __init__ (self, primary, derived, averaged):
+        self.primary = primary
+        self.derived = derived
+        self.averaged = averaged
+
+    def varlist(self, tree):
+        for v in tree.children:
+            self.primary.add(v.value)
+
+    def assign_var (self, tree):
+        lval, rval = tree.children
+
+        if lval.value in self.derived:
+            raise StandardError("duplicate definition of " + lval)
+        self.derived[lval.value] = Field(lval.value, rval, self.derived)
+
+    def assign_avg_var (self, tree):
+        w = tree.children[0]
+        targets = tree.children[1:]
+
+        try:
+            self.averaged[w.children[0].value] = set([x.value for x in targets])
+        except IndexError:
+            self.averaged[None] = set([x.value for x in targets])
+
+class Stage1():
+    ''' conversion from tree to python data '''
+
+    def __init__ (self, raw_tree):
+        self.primary = set([])
+        self.derived = {}
+        self.averaged = {}
+        CollectDefinitions( self.primary, self.derived, self.averaged ).visit(raw_tree)
+
+    def __repr__ (self):
+        return "\n".join(map(str, [self.primary, self.derived, self.averaged]))
+
+class Stage2():
+    ''' expand derivatives '''
+
+    def __init__ (self, src):
+        self.src = src
+        self.derived = src.derived
+        self.derivative = {}
+
+        dset = set([])
+        for k, v in self.derived.iteritems():
+            dset.update(v.derivs)
+
+        for tup in dset:
+            self.derivative[tup] = DerivedField(tup[0], tup[1], self.derived)
+
+    def __repr__ (self):
+        return "\n".join(map(str, [self.derived, self.derivative]))
+
+
+
+class Stage3():
+    ''' analyze fluctuation '''
+
+class Stage4():
+    ''' pass1 and pass2 seperation and calculation ordering '''
+
+class Stage5():
+    ''' analyze liveness and allocate array '''
+
+class Stage6():
+    ''' generate fortran code '''