update reader and implement singletons

lib/ast/basic_expressions.rb

@@ -9,6 +9,22 @@ module Ast
     end
   end
 
+  class TrueExpression
+    def compile frame
+      Virtual::TrueValue.new
+    end
+  end
+  class FalseExpression
+    def compile frame
+      Virtual::FalseValue.new
+    end
+  end
+  class NilExpression
+    def compile frame
+      Virtual::NilValue.new
+    end
+  end
+
   class NameExpression < Expression
 #    attr_reader  :name
 

lib/virtual/constants.rb

@@ -1,7 +1,6 @@
 module Virtual
   
   class Constant < ::Virtual::Object
-    
   end
 
   # another abstract "marker" class (so we can check for it)

lib/virtual/mystery.rb

@@ -1,6 +1,6 @@
 module Virtual
   class Mystery < Value
-    def initilize 
+    def initialize 
     end
 
     def as type
@@ -8,4 +8,11 @@ module Virtual
     end
 
   end
+
+  class TrueValue < Value
+  end
+  class FalseValue < Value
+  end
+  class NilValue < Value
+  end
 end

lib/virtual/value.rb

@@ -6,6 +6,12 @@ module Virtual
   # Integer and (Object) References are the main derived classes, but float will come and ...
   # The Mystery Value has unknown type and has only casting methods. So it must be cast to be useful.
   class Value
+    def == other
+      other.class == self.class
+    end
+    def inspect
+      self.class.name + ".new()"
+    end
     def type
       self.class
     end