fixed rubout and reinsertion of the loop end command (>)

 * the loop counter wasn't properly restored when rubbing out
   the loop end command, so when it was reinserted again,
   it would still be 1 (since that's the abortion criteria) and
   no additional loop iteration was performed.
 * simple test case: Try typing 5<%a> then rubout and reinsert ">".
 * Fixed by saving the loop counter before modifying it.
   There are arguably more efficient ways to do this like only
   creating one undo token at the end of the loop -- but that
   would require storing the initial loop counter in the LoopContext
   and would generally be more tricky.
 * The case of infinite loops has been optimized in interactive mode:
   Since the loop counter never actually changes, we do not have
   to create an undo token per loop iteration.

1 files changed, 11 insertions, 2 deletions

diff --git a/src/parser.cpp b/src/parser.cpp
index 85d455c..f05f167 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -1024,9 +1024,18 @@ StateStart::custom(gchar chr)
 					expressions.brace_close();
 				LoopStack::undo_push<loop_stack>(loop_stack.pop());
 			} else {
-				/* repeat loop */
+				/*
+				 * Repeat loop:
+				 * NOTE: One undo token per iteration could
+				 * be avoided by saving the original counter
+				 * in the LoopContext.
+				 * We do however optimize the case of infinite loops
+				 * because the loop counter does not have to be
+				 * updated.
+				 */
 				macro_pc = ctx.pc;
-				ctx.counter = MAX(ctx.counter - 1, -1);
+				if (ctx.counter >= 0)
+					undo.push_var(ctx.counter) = ctx.counter - 1;
 			}
 		}
 		break;