finishes the yellow world instructions

lib/interpreter.rb

@@ -2,12 +2,22 @@
 require "eventable"
 
 class Interpreter
+  # fire events for changed pc and register contents
   include Eventable
 
-  attr_accessor :instruction
-  attr_accessor :link
-  attr_accessor :block
+  # current instruction or pc
+  attr_reader :instruction
+
+  # an (arm style) link register. store the return address to return to
+  attr_reader :link
+
+  # current executing block. since this is not a hardware simulator this is luxury
+  attr_reader :block
+
+  # the registers, 12
   attr_reader :registers
+
+  # collect the output
   attr_reader :stdout
 
   def initialize
@@ -54,6 +64,7 @@ class Interpreter
   end
 
   def tick
+    return unless @instruction
     name = @instruction.class.name.split("::").last
     fetch = send "execute_#{name}"
     return unless fetch
@@ -130,9 +141,21 @@ class Interpreter
       str = object_for( :r1 ) # should test length, ie r2
       raise "NO string for putstring #{str}" unless str.is_a? Symbol
       @stdout += str.to_s
+    when :exit
+      @instruction = nil
+      return false
     else
       raise "un-implemented syscall #{name}"
     end
     true
   end
+
+  def execute_FunctionReturn
+    object = object_for( @instruction.register )
+    #wouldn't need to assign to link, but makes tsting easier
+    @link = object.internal_object_get( @instruction.index )
+    @block , @instruction = @link
+    # we jump back to the call instruction. so it is as if the call never happened and we continue
+    true
+  end
 end

test/interpreter_test.rb

@@ -53,10 +53,12 @@ class InterpreterTest < MiniTest::Test
     ["Branch" , "LoadConstant" , "GetSlot" , "SetSlot" , "RegisterTransfer" ,
      "GetSlot" , "FunctionCall" , "SaveReturn" , "LoadConstant"  , "SetSlot" ,
      "GetSlot" ,  "GetSlot" , "SetSlot" , "LoadConstant" , "SetSlot" ,
-     "RegisterTransfer" ,  "GetSlot" ,  "FunctionCall" , "SaveReturn" ,
-     "RegisterTransfer" , "Syscall"].each_with_index do |name , index|
+     "RegisterTransfer" ,  "GetSlot" ,  "FunctionCall" , "SaveReturn" , "RegisterTransfer" ,
+     "Syscall" , "RegisterTransfer" , "RegisterTransfer" , "SetSlot" , "GetSlot" ,
+     "GetSlot" , "RegisterTransfer" ,"GetSlot" , "GetSlot","GetSlot",
+     "FunctionReturn" , "RegisterTransfer" , "Syscall" , "NilClass"].each_with_index do |name , index|
       got = ticks(1)
-      assert got.class.name.index(name) , "Wrong class for #{index}, expect #{name} , got #{got}"
+      assert got.class.name.index(name) , "Wrong class for #{index+1}, expect #{name} , got #{got}"
     end
   end
 
@@ -66,4 +68,15 @@ class InterpreterTest < MiniTest::Test
     assert_equal "Hello again" , @interpreter.stdout
   end
 
+  def test_return
+    done = ticks(31)
+    assert_equal Register::FunctionReturn ,  done.class
+    assert @interpreter.block.is_a?(Virtual::Block)
+    assert @interpreter.instruction.is_a?(Register::Instruction) , "not instruction #{@interpreter.instruction}"
+  end
+
+  def test_exit
+    done = ticks(34)
+    assert_equal NilClass ,  done.class
+  end
 end