start delegating scope matters to the compiler(s)

slot_type_for to return the slot way to access variable
this is off course version 0.0.1 alpha, no types are checked or errors handled

lib/risc/method_compiler.rb

@@ -47,10 +47,28 @@ module Risc
       self.new(method)
     end
 
+    # determine how given name need to be accsessed.
+    # For methods the options are args or frame
+    def slot_type_for(name)
+      if @method.arguments_type.variable_index(name)
+        type = :arguments
+      else
+        type = :frame
+      end
+      [type , name]
+    end
+
     def add_block_compiler(compiler)
       @block_compilers << compiler
     end
 
+    # return true or false if the given name is in scope (arg/local)
+    def in_scope?(name)
+      ret = true if @method.arguments_type.variable_index(name)
+      ret = @method.frame_type.variable_index(name) unless ret
+      ret
+    end
+
     # convert the given mom instruction to_risc and then add it (see add_code)
     # continue down the instruction chain unti depleted
     # (adding moves the insertion point so the whole mom chain is added as a risc chain)