remove unused methods

and a whole lot more index fixes

lib/risc/instructions/getter.rb

@@ -22,7 +22,7 @@ module Risc
       @array = array
       @index = index
       @register = register
-      raise "index 0 " if index == 0
+      raise "index #{index}" if index.is_a?(Numeric) and index < 0
       raise "Not integer or reg #{index}" unless index.is_a?(Numeric) or RiscValue.look_like_reg(index)
       raise "Not register #{register}" unless RiscValue.look_like_reg(register)
       raise "Not register #{array}" unless RiscValue.look_like_reg(array)