diff --git a/Parser.lua b/Parser.lua
index aad3da8..b80761d 100644
--- a/Parser.lua
+++ b/Parser.lua
@@ -1,6 +1,4 @@
 
-require 'errors' 'shunt' . enable_strict_globals ()
-
 ---- Algorithm
 
 local DEFAULT_ASSOC = 'left'
diff --git a/assert-gooder.lua b/assert-gooder.lua
index 46af4f4..f874795 100644
--- a/assert-gooder.lua
+++ b/assert-gooder.lua
@@ -251,6 +251,26 @@ local function for_each_node_in_ast (ast, func)
     return func(ast)
 end
 
+local CONSTANT_OP = {}
+
+function CONSTANT_OP.DOT     (node)  return node[1].value[ node[2].value ]  end -- TODO
+function CONSTANT_OP.AND     (node)  return node[1].value and node[2].value end
+function CONSTANT_OP.OR      (node)  return node[1].value or  node[2].value end
+function CONSTANT_OP.PLUS    (node)  return node[1].value + node[2].value end
+function CONSTANT_OP.MINUS   (node)  return node[1].value - node[2].value end
+function CONSTANT_OP.TIMES   (node)  return node[1].value * node[2].value end
+function CONSTANT_OP.DIVIDE  (node)  return node[1].value / node[2].value end
+function CONSTANT_OP.MODULO  (node)  return node[1].value % node[2].value end
+function CONSTANT_OP.CARET   (node)  return node[1].value ^ node[2].value end
+function CONSTANT_OP.HASHTAG (node)  return #node[1].value  end
+function CONSTANT_OP.EQ      (node)  return node[1].value == node[2].value end
+function CONSTANT_OP.NEQ     (node)  return node[1].value ~= node[2].value end
+function CONSTANT_OP.LEQ     (node)  return node[1].value <= node[2].value end
+function CONSTANT_OP.GEQ     (node)  return node[1].value >= node[2].value end
+function CONSTANT_OP.LE      (node)  return node[1].value <  node[2].value end
+function CONSTANT_OP.GT      (node)  return node[1].value >  node[2].value end
+function CONSTANT_OP.CONCAT  (node)  return node[1].value .. node[2].value end
+
 local function populate_ast_with_semantics (ast, info)
     assert(type(ast) == 'table')
     assert(type(info) == 'table')
@@ -260,16 +280,20 @@ local function populate_ast_with_semantics (ast, info)
             node.exp, node.token  =  node.token, nil
         end
     end)
+
     return for_each_node_in_ast(ast, function(node)
         if node.exp == 'IDENTIFIER' then
             node.value, node.scope, node.function_local  =  get_variable(node.text, info)
         elseif CONSTANT_VALUE_TOKEN[node.exp] then
             node.value = CONSTANT_VALUE_TOKEN[node.exp](node.text)
-        elseif node.exp == 'OP' and node.binop == 'DOT' then
-            assert(node[1].value and node[2].value)
-            node.value =  node[1].value[ node[2].value ] --TODO
+            node.is_constant = true
+        elseif node.exp == 'OP' and CONSTANT_OP[node.binop] and node[1].value and node[2] and node[2].value then
+            assert(node[1].value and (not node[2] or node[2].value))
+            node.value       = CONSTANT_OP[node.binop](node)
+            node.is_constant = node[1].is_constant and (not node[2] or node[2].is_constant)
         end
     end)
+
 end
 
 --------------------------------------------------------------------------------
diff --git a/test/tests.lua b/test/tests.lua
index 17bce2c..38d494c 100644
--- a/test/tests.lua
+++ b/test/tests.lua
@@ -5,3 +5,4 @@ local TEST_SUITE = require "TestSuite" 'assert-gooder'
       TEST_SUITE:addModules 'test/test_*.lua'
       TEST_SUITE:enableStrictGlobal()
       TEST_SUITE:runTests()
+