From 21e426be712880729255652a1f07064d509f6653 Mon Sep 17 00:00:00 2001
From: Torsten Ruger <torsten@villataika.fi>
Date: Wed, 12 Apr 2017 14:45:02 +0300
Subject: [PATCH] finishes local assignments to_mom

---
 lib/mom/slot_load.rb                        | 40 +++++++++++++++++++++
 lib/vool/statements/assignment_statement.rb |  4 ++-
 test/vool/to_mom/test_assignemnt.rb         | 22 ++++++++++--
 3 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/lib/mom/slot_load.rb b/lib/mom/slot_load.rb
index 267c12d6..19e31cfd 100644
--- a/lib/mom/slot_load.rb
+++ b/lib/mom/slot_load.rb
@@ -1,6 +1,46 @@
 module Mom
 
+  # SlotLoad is an abstract base class for moving data into a slot
+  # A Slot is the basically an instance variable, but it must be of known type
+  #
+  # The value loaded can be a constant (SlotConstant) or come from another Slot (SlotMove)
+  #
+  # The Slot is the left hand side, the right hand side being determined by the subclass.
+  # The only known object (*) for the left side is the current message, which is a bit like
+  # the oo version of a PC (program Counter)
+  # (* off course all class objects are global, and so they are allowed too)
+  #
+  # A maybe not immediately obvious corrolar of this design is the total absence of
+  # general purpose instance variable accessors. Ie only inside an object's functions
+  # can a method access instance variables, because only inside the method is the type
+  # guaranteed.
+  # From the outside a send is neccessary, both for get and set, (which goes through the method
+  # resolution and guarantees the correct method for a type), in other words perfect data hiding.
+  #
+  # @left: is an array of symbols, that specifies the first the object, and then the Slot.
+  #        The first element is either a known type name (Capitalized symbol of the class name) ,
+  #        or the symbol :message
+  #        Ant subsequent symbols must be instance variables on the previous type.
+  #        Examples:  [:message , :self] or [:Space : :next_message]
+  #
+  # @right: depends on the derived Class
+  #
   class SlotLoad < Instruction
+    attr_reader :left , :right
+    def initialize(left , right)
+      @left , @right = left , right
+    end
   end
 
+  # A SlotConstant moves a constant into a know Slot.
+  # Eg when you write a = 5 , the 5 becomes a constant, and so the right side
+  # the a is an instance variable on the current frame, and the frame is an instance
+  # of the current message, so the effect is something like message.frame.a = 5
+  # @left:  See SlotLoad, and array of symbols
+  # @right: A Constant from parse, ie an instance of classes in basc_value, like TrueStatement
+  class SlotConstant < SlotLoad
+  end
+
+  class SlotMove < SlotLoad
+  end
 end
diff --git a/lib/vool/statements/assignment_statement.rb b/lib/vool/statements/assignment_statement.rb
index 36fcd523..df17cc05 100644
--- a/lib/vool/statements/assignment_statement.rb
+++ b/lib/vool/statements/assignment_statement.rb
@@ -14,10 +14,12 @@ module Vool
     def add_local( array )
       array << @name
     end
+
     def to_mom( method )
-      Mom::SlotLoad.new
+      Mom::SlotConstant.new([:message , :self , @name] , @value)
     end
   end
+        
   class InstanceAssignment < Assignment
     # used to collect type information
     def add_ivar( array )
diff --git a/test/vool/to_mom/test_assignemnt.rb b/test/vool/to_mom/test_assignemnt.rb
index 8bc16b86..e0ea77d7 100644
--- a/test/vool/to_mom/test_assignemnt.rb
+++ b/test/vool/to_mom/test_assignemnt.rb
@@ -6,6 +6,7 @@ module Vool
 
     def setup
       Risc.machine.boot
+      @method = compile_first_method( "a = 5")
     end
 
     def compile_first_method input
@@ -17,8 +18,25 @@ module Vool
     end
 
     def test_class_compiles
-      meth = compile_first_method( "a = 5")
-      assert_equal Mom::SlotLoad , meth.first.class , meth
+      assert_equal Mom::SlotConstant , @method.first.class , @method
+    end
+    def test_slot_is_set
+      assert @method.first.left
+    end
+    def test_slot_starts_at_message
+      assert_equal :message , @method.first.left[0]
+    end
+    def test_slot_gets_self
+      assert_equal :self , @method.first.left[1]
+    end
+    def test_slot_assigns_to_local
+      assert_equal :a , @method.first.left[-1]
+    end
+    def test_slot_assigns_something
+      assert @method.first.right
+    end
+    def test_slot_assigns_int
+      assert_equal IntegerStatement ,  @method.first.right.class
     end
   end
 end