add deletion to compare-testing (deletion does not work properly yet, as expected)

tests/compare_to_rope.sml

@@ -1,6 +1,6 @@
 structure CompareToRope =
 struct
-fun compareTxns arr =
+  fun compareTxns arr =
     Vector.foldli
       (fn (idx, (pos, delNum, insStr), (rope, gapBuffer)) =>
          let
@@ -8,9 +8,14 @@ fun compareTxns arr =
            val oldRope = rope
            val strSize = String.size insStr
 
+           val rope =
+             if delNum > 0 then TinyRope.delete (pos, delNum, rope) else rope
            val rope =
              if strSize > 0 then TinyRope.insert (pos, insStr, rope) else rope
 
+           val gapBuffer =
+             if delNum > 0 then LineGap.delete (pos, delNum, gapBuffer)
+             else gapBuffer
            val gapBuffer =
              if strSize > 0 then LineGap.insert (pos, insStr, gapBuffer)
              else gapBuffer