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

@@ -1,14 +1,26 @@
+# pops the top item from the +:code+ stack;
+# implements a equivalent to Lisp's +cdr+ function, treating Nudge blocks as lists:
+#
+# If the +:code+ value has at least 2 points (meaning it's a block with at least 1 element),
+# the new code value is this block with its first element deleted; otherwise, the result is
+# an empty block.
+#
+# *needs:* 1 +:code+
+#
+# *pushes:* 1 +:code+
+#
+
 class CodeCdrInstruction < Instruction
   def preconditions?
     needs :code, 1
   end
   def setup
     @arg = @context.pop_value(:code)
   end
   def derive
     tree = NudgeProgram.new(@arg)
-    if tree.linked_code.kind_of?(CodeblockPoint) && (tree.points > 2)
+    if tree.linked_code.kind_of?(CodeblockPoint) && (tree.points > 1)
       new_tree = tree.delete_point(2)
     else
       new_tree = CodeblockPoint.new([])
     end
     @result = ValuePoint.new("code", new_tree.blueprint)