diff --git a/lib/bosl/compiler.rb b/lib/bosl/compiler.rb
index bea82d45..baed2044 100644
--- a/lib/bosl/compiler.rb
+++ b/lib/bosl/compiler.rb
@@ -1,6 +1,13 @@
 module Bosl
-  module Compiler
+  class Compiler < AST::Processor
+    attr_reader :method
 
+    def initialize(method)
+      @method = method
+    end
+    def handler_missing node
+      raise "No handler  on_#{node.type}(node)"
+    end
     # Compiling is the conversion of the AST into 2 things:
     # - code (ie sequences of Instructions inside Blocks) carried by MethodSource
     # - an object graph containing all the Methods, their classes and Constants
@@ -13,15 +20,14 @@ module Bosl
     # The compile method (so every compile method) returns the value that it deposits which
     # may be unknown Unknown value.
     #
-    # The Compiler.compile uses a visitor patter to dispatch according to the class name of
-    # the expression. So a NameExpression is delegated to Virtual::Set.new etc.
+    # The process uses a visitor pattern (from AST::Processor) to dispatch according to the
+    # type the expression. So a s(:if xx) will become an on_if(node) call.
     # This makes the dispatch extensible, ie Expressions may be added by external code,
     # as long as matching compile methods are supplied too.
     #
     def self.compile expression , method
-      exp_name = expression.type
-      puts "Expression #{expression.to_sexp}"
-      self.send "compile_#{exp_name}".to_sym , expression, method
+      compiler = Compiler.new method
+      compiler.process expression
     end
 
   end
diff --git a/lib/bosl/compiler/basic_expressions.rb b/lib/bosl/compiler/basic_expressions.rb
index e10b9f39..3ca82285 100644
--- a/lib/bosl/compiler/basic_expressions.rb
+++ b/lib/bosl/compiler/basic_expressions.rb
@@ -1,7 +1,7 @@
 module Bosl
   # collection of the simple ones, int and strings and such
 
-  module Compiler
+  Compiler.class_eval do
 
     # Constant expressions can by definition be evaluated at compile time.
     # But that does not solve their storage, ie they need to be accessible at runtime from _somewhere_
@@ -12,32 +12,32 @@ module Bosl
     # But in the future (in the one that holds great things) we optimize those unneccesay moves away
 
   #    attr_reader :value
-      def self.compile_int expression , method
+      def on_int expression
         int = *expression
         to =  Virtual::Return.new(Integer , int)
         method.source.add_code Virtual::Set.new( int , to )
         to
       end
 
-      def self.compile_true expression , method
+      def on_true expression
         to = Virtual::Return.new(Reference , true )
         method.source.add_code Virtual::Set.new( true , to )
         to
       end
 
-      def self.compile_false expression , method
+      def on_false expression
         to = Virtual::Return.new(Reference , false)
         method.source.add_code Virtual::Set.new( false , to )
         to
       end
 
-      def self.compile_nil expression , method
+      def on_nil expression
         to = Virtual::Return.new(Reference , nil)
         method.source.add_code Virtual::Set.new( nil , to )
         to
       end
 
-      def self.compile_modulename expression , method
+      def on_modulename expression
         clazz = Parfait::Space.object_space.get_class_by_name expression.name
         raise "compile_modulename #{clazz}.#{name}" unless clazz
         to = Virtual::Return.new(Reference , clazz )
@@ -46,7 +46,7 @@ module Bosl
       end
 
   #    attr_reader  :string
-      def self.compile_string expression , method
+      def on_string expression
         # Clearly a TODO here to implement strings rather than reusing symbols
         value = expression.first.to_sym
         to = Virtual::Return.new(Virtual::Reference , value)
@@ -56,11 +56,11 @@ module Bosl
       end
 
       #attr_reader  :left, :right
-      def self.compile_assignment expression , method
+      def on_assignment expression
         unless expression.left.instance_of? Ast::NameExpression
           raise "must assign to NameExpression , not #{expression.left}"
         end
-        r = Compiler.compile(expression.right , method )
+        r = process(expression.right  )
         raise "oh noo, nil from where #{expression.right.inspect}" unless r
         index = method.has_arg(expression.left.name.to_sym)
         if index
@@ -72,7 +72,7 @@ module Bosl
         r
       end
 
-      def self.compile_variable expression, method
+      def on_variable expression
         method.source.add_code InstanceGet.new(expression.name)
         Virtual::Return.new( Unknown )
       end
diff --git a/lib/bosl/compiler/callsite_expression.rb b/lib/bosl/compiler/callsite_expression.rb
index a9d3e82e..1cef5b25 100644
--- a/lib/bosl/compiler/callsite_expression.rb
+++ b/lib/bosl/compiler/callsite_expression.rb
@@ -1,15 +1,15 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
   # operators are really function calls
 
 #    call_site - attr_reader  :name, :args , :receiver
 
-    def self.compile_call expession , method
+    def on_call expession 
       name , arguments , receiver = *expession
       name = name.to_a.first
 
       if receiver
-        me = Compiler.compile( receiver.to_a.first , method )
+        me = process( receiver.to_a.first  )
       else
         me = Virtual::Self.new
       end
@@ -21,7 +21,7 @@ module Bosl
       compiled_args = []
       arguments.to_a.each_with_index do |arg , i|
         #compile in the running method, ie before passing control
-        val = Compiler.compile( arg , method)
+        val = process( arg)
         # move the compiled value to it's slot in the new message
         # + 1 as this is a ruby 0-start , but 0 is the last message ivar.
         # so the next free is +1
diff --git a/lib/bosl/compiler/compound_expressions.rb b/lib/bosl/compiler/compound_expressions.rb
index c0fcdaf9..2b45a60b 100644
--- a/lib/bosl/compiler/compound_expressions.rb
+++ b/lib/bosl/compiler/compound_expressions.rb
@@ -1,15 +1,15 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 
 #    attr_reader :values
-    def self.compile_array expession, context
+    def on_array expession, context
 #      to.do
     end
 #    attr_reader :key , :value
-    def self.compile_association context
+    def on_association context
 #      to.do
     end
-    def self.compile_hash context
+    def on_hash context
 #      to.do
     end
   end
diff --git a/lib/bosl/compiler/expression_list.rb b/lib/bosl/compiler/expression_list.rb
index 759a3470..83d7a7e0 100644
--- a/lib/bosl/compiler/expression_list.rb
+++ b/lib/bosl/compiler/expression_list.rb
@@ -1,10 +1,8 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 #    list - attr_reader  :expressions
-    def self.compile_expressions expession , method
-      expession.children.collect do |part|
-        Compiler.compile(  part , method )
-      end
+    def on_expressions expession
+      process_all(  expession.children  )
     end
   end
 end
diff --git a/lib/bosl/compiler/function_expression.rb b/lib/bosl/compiler/function_expression.rb
index a3299ce9..b03a886c 100644
--- a/lib/bosl/compiler/function_expression.rb
+++ b/lib/bosl/compiler/function_expression.rb
@@ -1,7 +1,7 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 #    function attr_reader  :name, :params, :body , :receiver
-    def self.compile_function  expression, method
+    def on_function  expression
       return_type , name , parameters, kids = *expression
       name =  name.to_a.first
       args = parameters.to_a.collect do |p|
@@ -11,7 +11,7 @@ module Bosl
 
       if expression[:receiver]
         # compiler will always return slot. with known value or not
-        r = Compiler.compile(expression.receiver, method )
+        r = process(expression.receiver )
         if( r.value.is_a? Parfait::Class )
           class_name = r.value.name
         else
@@ -25,11 +25,15 @@ module Bosl
       new_method.source.receiver = r
       new_method.for_class.add_instance_method new_method
 
+      old_method = @method
+      @method = new_method
+
       #frame = frame.new_frame
       kids.to_a.each do |ex|
-        return_type = Compiler.compile(ex,new_method  )
+        return_type = process(ex)
         raise return_type.inspect if return_type.is_a? Virtual::Instruction
       end
+      @method = old_method
       new_method.source.return_type = return_type
       Virtual::Return.new(return_type)
     end
diff --git a/lib/bosl/compiler/if_expression.rb b/lib/bosl/compiler/if_expression.rb
index f7fd1f2b..93c86032 100644
--- a/lib/bosl/compiler/if_expression.rb
+++ b/lib/bosl/compiler/if_expression.rb
@@ -1,8 +1,8 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 #    if - attr_reader  :cond, :if_true, :if_false
 
-    def self.compile_if expression , method
+    def on_if expression
       condition , if_true , if_false = *expression
       condition = condition.first
       # to execute the logic as the if states it, the blocks are the other way around
@@ -13,7 +13,7 @@ module Bosl
       false_block = method.source.new_block "if_false"    # directly next in order, ie if we don't jump we land here
 
 
-      is = Compiler.compile(condition, method )
+      is = process(condition )
       # TODO should/will use different branches for different conditions.
       # just a scetch : cond_val = cond_val.is_true?(method) unless cond_val.is_a? BranchCondition
       method.source.add_code Virtual::IsTrueBranch.new( true_block )
@@ -21,18 +21,11 @@ module Bosl
       # compile the true block (as we think of it first, even it is second in sequential order)
       method.source.current true_block
       last = is
-      if_true.each do |part|
-        last = Compiler.compile(part,method  )
-        raise part.inspect if last.nil?
-      end
+      last = process_all(if_true).last
 
       # compile the false block
       method.source.current false_block
-      if_false.each do |part|
-        #puts "compiling in if false #{part}"
-        last = Compiler.compile(part,method )
-        raise part.inspect if last.nil?
-      end
+      last = process_all(if_false).last
       method.source.add_code Virtual::UnconditionalBranch.new( merge_block )
 
       #puts "compiled if: end"
diff --git a/lib/bosl/compiler/module_expression.rb b/lib/bosl/compiler/module_expression.rb
index aa6b0ded..f82501bd 100644
--- a/lib/bosl/compiler/module_expression.rb
+++ b/lib/bosl/compiler/module_expression.rb
@@ -1,11 +1,11 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 #    module attr_reader  :name ,:expressions
-    def self.compile_module expression , context
+    def on_module expression 
       return clazz
     end
 
-    def self.compile_class expression , method
+    def on_class expression
       clazz = Parfait::Space.object_space.get_class_by_name! expression.name
       #puts "Compiling class #{clazz.name.inspect}"
       expression_value = nil
@@ -15,7 +15,7 @@ module Bosl
         #  ie throw an error for now
         raise "only functions for now #{expr.inspect}" unless expr.is_a? Ast::FunctionExpression
         #puts "compiling expression #{expression}"
-        expression_value = Compiler.compile(expr,method  )
+        expression_value = process(expr  )
         #puts "compiled expression #{expression_value.inspect}"
       end
 
diff --git a/lib/bosl/compiler/name_expression.rb b/lib/bosl/compiler/name_expression.rb
index 404ac3a8..1ce1a62c 100644
--- a/lib/bosl/compiler/name_expression.rb
+++ b/lib/bosl/compiler/name_expression.rb
@@ -1,11 +1,11 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 
       #    attr_reader  :name
       # compiling name needs to check if it's a variable and if so resolve it
       # otherwise it's a method without args and a send is issued.
       # whichever way this goes the result is stored in the return slot (as all compiles)
-      def self.compile_name expression , method
+      def on_name expression 
         name = expression.to_a.first
         return Virtual::Self.new( Reference.new(method.for_class)) if name == :self
         # either an argument, so it's stored in message
diff --git a/lib/bosl/compiler/operator_expressions.rb b/lib/bosl/compiler/operator_expressions.rb
index 2140be60..4b1afa75 100644
--- a/lib/bosl/compiler/operator_expressions.rb
+++ b/lib/bosl/compiler/operator_expressions.rb
@@ -1,17 +1,17 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 #    operator attr_reader  :operator, :left, :right
-    def self.compile_operator expression, method
+    def on_operator expression
       operator , left , right = *expression
       nil
     end
 
-    def self.compile_assign expression, method
+    def on_assign expression
       puts "assign"
       puts expression.inspect
       name , value = *expression
       name = name.to_a.first
-      v = self.compile(value , method )
+      v = process(value  )
       index = method.ensure_local( name )
       method.source.add_code Virtual::Set.new(Virtual::FrameSlot.new(index ) , v )
     end
diff --git a/lib/bosl/compiler/return_expression.rb b/lib/bosl/compiler/return_expression.rb
index 48591d55..848b71dd 100644
--- a/lib/bosl/compiler/return_expression.rb
+++ b/lib/bosl/compiler/return_expression.rb
@@ -1,9 +1,9 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 
 #    return attr_reader  :expression
-    def self.compile_return expression, method
-      return Compiler.compile(expression.to_a.first , method)
+    def on_return expression
+      return process(expression.to_a.first )
     end
   end
 end
diff --git a/lib/bosl/compiler/while_expression.rb b/lib/bosl/compiler/while_expression.rb
index e2e4b361..9b3ee207 100644
--- a/lib/bosl/compiler/while_expression.rb
+++ b/lib/bosl/compiler/while_expression.rb
@@ -1,21 +1,21 @@
 module Bosl
-  module Compiler
+  Compiler.class_eval do
 
 #    while- attr_reader  :condition, :body
-    def self.compile_while expression, method
+    def on_while expression
       # this is where the while ends and both branches meet
       merge = method.source.new_block("while merge")
       # this comes after the current and beofre the merge
       start = method.source.new_block("while_start" )
       method.source.current start
 
-      cond = Compiler.compile(expression.condition, method)
+      cond = process(expression.condition)
 
       method.source.add_code IsTrueBranch.new(merge)
 
       last = cond
       expression.body.each do |part|
-        last = Compiler.compile(part , method)
+        last = process(part)
         raise part.inspect if last.nil?
       end
       # unconditionally branch to the start
diff --git a/lib/salama.rb b/lib/salama.rb
index efbdad0b..8136754d 100644
--- a/lib/salama.rb
+++ b/lib/salama.rb
@@ -4,11 +4,6 @@ require "stream_reader"
 require "elf/object_writer"
 require 'salama-reader'
 AST::Node.class_eval do
-  def each
-    children.each do |child|
-      yield child
-    end
-  end
   def first
     children.first
   end
diff --git a/test/compiler/compiler_helper.rb b/test/compiler/compiler_helper.rb
index 89eedfc5..5014cba4 100644
--- a/test/compiler/compiler_helper.rb
+++ b/test/compiler/compiler_helper.rb
@@ -2,7 +2,7 @@ require_relative '../helper'
 require 'parslet/convenience'
 
 
-module CompilerHelper
+Compiler.class_eval doHelper
 
   def check
     Virtual.machine.boot.compile_main @string_input
diff --git a/test/compiler/test_compiler.rb b/test/compiler/test_compiler.rb
index 1dc5e5ad..6ed18584 100644
--- a/test/compiler/test_compiler.rb
+++ b/test/compiler/test_compiler.rb
@@ -6,7 +6,7 @@ class CompilerTest < MiniTest::Test
     Virtual.machine.boot
   end
   def check
-    res = Virtual::Compiler.compile( @expression , Virtual.machine.space.get_main )
+    res = Bosl::Compiler.compile( @expression , Virtual.machine.space.get_main )
     assert res.is_a?(Virtual::Slot) , "compiler must compile to slot, not #{res.class}"
   end
   def true_ex
diff --git a/test/fragments/helper.rb b/test/fragments/helper.rb
index 7942a8b7..07697d96 100644
--- a/test/fragments/helper.rb
+++ b/test/fragments/helper.rb
@@ -8,9 +8,11 @@ module Fragments
 
   def check
     expressions = Virtual.machine.boot.compile_main @string_input
+    puts expressions
     @expect.each_with_index do | should , i |
-      assert expressions[i].is_a?(Virtual::Slot) , "compiles should return slots, not #{should.class}"
-      assert_equal should , expressions[i].class
+      exp_i = expressions[i]
+      assert exp_i.is_a?(Virtual::Slot) , "compiles should return #{should}, not #{exp_i}"
+      assert_equal should , exp_i.class
     end
 #    Virtual.machine.run_passes
   end
diff --git a/test/interpreter/test_add.rb b/test/interpreter/test_add.rb
index 80849ca7..33f37857 100644
--- a/test/interpreter/test_add.rb
+++ b/test/interpreter/test_add.rb
@@ -5,7 +5,7 @@ class AddTest < MiniTest::Test
   def setup
     Virtual.machine.boot
     code =Ast::OperatorExpression.new("+", Ast::IntegerExpression.new(2),Ast::IntegerExpression.new(5))
-    Virtual::Compiler.compile( code , Virtual.machine.space.get_main )
+    Bosl::Compiler.compile( code , Virtual.machine.space.get_main )
     Virtual.machine.run_before "Register::CallImplementation"
     @interpreter = Interpreter::Interpreter.new
     @interpreter.start Virtual.machine.init
diff --git a/test/interpreter/test_puts.rb b/test/interpreter/test_puts.rb
index b9068804..c8bc28a6 100644
--- a/test/interpreter/test_puts.rb
+++ b/test/interpreter/test_puts.rb
@@ -5,7 +5,7 @@ class TestPuts < MiniTest::Test
   def setup
     Virtual.machine.boot
     code = Ast::ExpressionList.new( [Ast::CallSiteExpression.new(:putstring, [] ,Ast::StringExpression.new("Hello again"))])
-    Virtual::Compiler.compile( code , Virtual.machine.space.get_main )
+    Bosl::Compiler.compile( code , Virtual.machine.space.get_main )
     Virtual.machine.run_before "Register::CallImplementation"
     @interpreter = Interpreter::Interpreter.new
     @interpreter.start Virtual.machine.init