lib/instructions/code/code_nth_point.rb in nudge-0.2.6 vs lib/instructions/code/code_nth_point.rb in nudge-0.2.7

@@ -1,21 +1,36 @@
+# pops the top +:code+ item and +:int+ item ("N");
+# pushes a new +:code+ item containing the Nth program point of the +:code+
+#
+# If the +:code+ is not a block, it's replaced intact;
+# if the +:code+ value cannot be parsed, an +:error+ is pushed instead of a +:code+ item;
+# otherwise, the index is chosen as +N+ modulo the length of the number of program points.
+#
+# *needs:* 1 +:code+ and 1 +:int+
+#
+# *pushes:* 1 +:code+
+#
+
 class CodeNthPointInstruction < Instruction # was CODE.EXTRACT in Push3
   def preconditions?
     needs :int, 1
     needs :code, 1
   end
+  
   def setup
     @arg1 = @context.pop_value(:int)
     @arg2 = @context.pop_value(:code)
   end
+  
   def derive
     tree = NudgeProgram.new(@arg2)
     tree_size = tree.points
     raise InstructionMethodError, "#{self.class} divied by zero" if tree_size < 1
     which = (@arg1-1) % tree_size + 1
     pt = tree[which]
     @result = ValuePoint.new("code", pt.blueprint)
   end
+  
   def cleanup
     pushes :code, @result
   end
 end