finish the idea behind #8, conditionally creating variables

by using space? , the ? makes for conditional creation of the variable
This is especially useful for constants (ie space)

lib/mom/instruction/message_setup.rb

@@ -64,8 +64,8 @@ module Mom
     # set the method into the message
     def build_message_data( builder )
       builder.build do
-        space! << Parfait.object_space
-        next_message! << space[:next_message]
+        space? << Parfait.object_space
+        next_message? << space[:next_message]
 
         #FIXME in a multithreaded future this should be done using lock free compare and swap.
         next_message_reg! << next_message[:next_message]
@@ -75,14 +75,6 @@ module Mom
         next_message[:caller] << message
         next_message[:method] << callable
 
-        # type << callable[:arguments_type]
-        # named_list << next_message[:arguments]
-        # named_list[:type] << type
-        #
-        # type << callable[:frame_type]
-        # named_list << next_message[:frame]
-        # named_list[:type] << type
-
       end
     end
   end

lib/risc/builder.rb

@@ -39,9 +39,16 @@ module Risc
         reg = Risc.label( @source , "#{name}_#{object_id}")
         @source_used = true
       else
-        raise "Must create (with !) before using #{name}" unless name[-1] == "!"
+        last_char = name[-1]
         name = name[0 ... -1]
-        #raise "name exists before being created #{name}" if @names.has_key?(name)
+        if last_char == "!" or last_char == "?"
+          if @names.has_key?(name)
+            return @names[name] if last_char == "?"
+            raise "Name exists before creating it #{name}#{last_char}"
+          end
+        else
+          raise "Must create (with ! or ?) before using #{name}#{last_char}"
+        end
         type = infer_type(name )
         reg = @compiler.use_reg( type.object_class.name ).set_builder(self)
       end
@@ -130,7 +137,7 @@ module Risc
       to.set_builder( self )    # esecially div10 comes in without having used builder
       from.set_builder( self )  # not named regs, different regs ==> silent errors
       build do
-        space! << Parfait.object_space
+        space? << Parfait.object_space
         to << space[:next_integer]
         integer_2! << to[:next_integer]
         space[:next_integer] << integer_2

test/risc/test_builder2.rb

@@ -25,6 +25,17 @@ module Risc
     def test_caller_reg
       assert_equal :Message , @builder.infer_type(:caller_reg).class_name
     end
+    def test_define_twice
+      @builder.caller_reg!
+      assert_raises{ @builder.caller_reg! }
+    end
+    def test_define_conditionally_first
+      assert_equal :r1 , @builder.caller_reg?.symbol
+    end
+    def test_define_conditionally_again
+      first = @builder.caller_reg!
+      assert_equal first , @builder.caller_reg?
+    end
     def test_caller_tmp
       assert_equal :Message , @builder.infer_type(:caller_tmp).class_name
     end