--- a/python/ppci/core/instruction.py	Tue Jan 01 17:17:44 2013 +0100
+++ b/python/ppci/core/instruction.py	Fri Jan 04 15:25:58 2013 +0100
@@ -1,15 +1,26 @@
 
 from .value import Value
 
+def Enum(**enums):
+   return type('Enum', (), enums)
+
 class Instruction(Value):
    """ Base class for all instructions. """
    pass
 
 class CallInstruction(Instruction):
-   pass
+   def __init__(self, callee, arguments):
+      super().__init__()
+      self.callee = callee
+      self.arguments = arguments
+
+BinOps = Enum(Add=1, Sub=2, Mul=3)
 
 class BinaryOperator(Instruction):
    def __init__(self, operation, value1, value2):
+      assert value1
+      assert value2
+      print('operation is in binops:', operation in BinOps)
       # Check types of the two operands:
       self.value1 = value1
       self.value2 = value2