add the simplest possible hash replacement with tests

lib/crystal.rb

@@ -4,4 +4,4 @@ require "elf/object_writer"
 require 'parser/crystal'
 require 'parser/transform'
 require "ast/all"
-require "vm/object_machine"
+require "virtual/machine"

lib/virtual/list.rb

@@ -0,0 +1,47 @@
+class List
+
+  def initialize
+    @next = nil
+  end
+  def empty?
+    @next.nil?
+  end
+
+  def get(key)
+    if( @next )
+      return @next.get(key)
+    else
+      return nil
+    end
+  end
+
+  def set(key , value)
+    if(@next)
+      @next.set(key,value)
+    else
+      @next = Node.new(key,value)
+    end
+    value
+  end
+end
+
+class Node < List
+  def initialize(key,value)
+    @key = key
+    @value = value
+  end
+  def get(key)
+    if(@key == key)
+      return @value
+    else
+      return super(key)
+    end
+  end
+  def set(key,value)
+    if(@key == key)
+      @value = value
+    else
+      super(key,value)
+    end
+  end
+end

lib/virtual/machine.rb

@@ -1,6 +1,8 @@
 module Vm
-  # The ObjectMachine is the object-oriented virtual machine in which ruby is implemented.
-  # 
+  # The Virtual Machine is a value based virtual machine in which ruby is implemented. While it is value based,
+  # it resembles oo in basic ways of object encapsulation and method invokation, it is a "closed" / static sytem
+  # in that all types are know and there is no dynamic dispatch (so we don't bite our tail here).
+  #
   # It is minimal and realistic and low level
   # - minimal means that if one thing can be implemented by another, it is left out. This is quite the opposite from
   #          ruby, which has several loops, many redundant if forms and the like.
@@ -9,25 +11,41 @@ module Vm
   # - low level means it's basic instructions are realively easily implemented in a register machine. ie send is not
   #   a an instruction but a function.
   #
-  # A better name may be Value-based machine. Ie all "objects" are values, all passing is value based.
-  # The illusion of objects is created by a value called object-reference.
-  #
   # So the memory model of the machine allows for indexed access into and "object" . A fixed number of objects exist
   # (ie garbage collection is reclaming, not destroying and recreating) although there may be a way to increase that number.
   #
-  # The ast is transformed to object-machine objects, some of which represent code, some data.
+  # The ast is transformed to virtaul-machine objects, some of which represent code, some data.
   # 
   # The next step transforms to the register machine layer, which is what actually executes. 
   #
 
-  # More concretely, an object machine is a sort of oo turing machine, it has a current instruction, executes the
-  # instructions, fetches the next one and so on.
+  # More concretely, an virtual machine is a sort of oo turing machine, it has a current instruction, executes the
+  # instructions, fetches the next one and so on. 
   # Off course the instructions are not soo simple, but in oo terms quite so.
   # 
+  # The machine is virtual in the sense that it is completely 
+  # modeled in software, it's complete state explicitly available (not implicitly by walking stacks or something)
+
   # The machine has a no register, but local variables, a scope at each point in time. 
   # Scope changes with calls and blocks, but is saved at each level. In terms of lower level implementation this means
-  # that the the model is such that what is a variable in ruby, never ends up being just on the cpu stack.
+  # that the the model is such that what is a variable in ruby, never ends up being just on the pysical stack.
   # 
-  class ObjectMachine
+  class Machine
+    # the main machine is the one that runs on the main thread, if it exists or receives an uncaught exception, that's it.
+    def self.main
+      @main  || @main = Machine.new
+    end
+
+    def initialize
+      # a binding represents the local variables at a point in the program.
+      # The amount of local variables is assumed to be relatively small, and so the 
+      # storage is a linked list. Has the same api as a ha
+      @bindings = List.new
+    end
+    def run instruction
+      instruction.execute
+    end
   end
 end
+
+require_relative "list"

test/unit/list.rb

@@ -0,0 +1,42 @@
+require_relative "../helper"
+
+class TestLists < MiniTest::Test
+
+  def setup
+    @list = List.new
+  end
+  def test_list_create
+    assert @list.empty?
+  end
+  def test_empty_list_doesnt_return
+    assert_equal nil , @list.get(3)
+    assert_equal nil , @list.get(:any)
+  end
+  def test_one_set1
+    assert_equal 1 , @list.set(1,1)
+  end
+  def test_one_set2
+    assert_equal :some , @list.set(1,:some)
+  end
+  def test_two_sets
+    assert_equal 1 , @list.set(1,1)
+    assert_equal :some , @list.set(1,:some)
+  end
+  def test_one_get1
+    test_one_set1
+    assert_equal 1 , @list.get(1)
+  end
+  def test_one_get2
+    test_one_set2
+    assert_equal :some , @list.get(1)
+  end
+  def test_many_get
+    shouldda  = { :one => 1 , :two => 2 , :three => 3}
+    shouldda.each do |k,v|
+      @list.set(k,v)
+    end
+    shouldda.each do |k,v|
+      assert_equal v , @list.get(k)
+    end
+  end
+end