when deleting inside pair, instead of searching either for either chr1 or chr2 and stopping at first match, search instead for openChr and closeChr, and keep an integer tracking what level of nesting we are at. This gives us the behaviour we want, which is to delete the pair at the correct level of nesting. When we encounter openChr, we increment the nesting counter by 1 and continue searching. When we encounter closeChr, if the nesting counter is 0, we return the current index, but if the nesting counter is higher than 0 when encounter closeChr, we decrement the nesting counter by 1 and continue searching.

fcore/cursor.sml

@@ -209,29 +209,61 @@ struct
 
   val toPrevChr = ToPrevChr.foldPrev
 
-  structure ToEitherChrNext =
+  structure ToCloseChrNext =
     MakeIfCharFolderNext
       (struct
-         type env = {chr1: char, chr2: char}
+         type env = {openChr: char, closeChr: char}
 
-         fun loop (strPos, str, absIdx, stl, chr1, chr2) =
+         fun loop (strPos, str, absIdx, stl, openChr, closeChr, openCount) =
            if strPos = String.size str then
              case stl of
-               str :: stl => loop (0, str, absIdx, stl, chr1, chr2)
+               str :: stl =>
+                 loop (0, str, absIdx, stl, openChr, closeChr, openCount)
              | [] => ~1
            else
              let
                val chr = String.sub (str, strPos)
              in
-               if chr = chr1 orelse chr = chr2 then absIdx
-               else loop (strPos + 1, str, absIdx + 1, stl, chr1, chr2)
+               if chr = openChr then
+                 loop
+                   ( strPos + 1
+                   , str
+                   , absIdx + 1
+                   , stl
+                   , openChr
+                   , closeChr
+                   , openCount + 1
+                   )
+               else if chr = closeChr then
+                 if openCount = 0 then
+                   absIdx
+                 else
+                   loop
+                     ( strPos + 1
+                     , str
+                     , absIdx + 1
+                     , stl
+                     , openChr
+                     , closeChr
+                     , openCount - 1
+                     )
+               else
+                 loop
+                   ( strPos + 1
+                   , str
+                   , absIdx + 1
+                   , stl
+                   , openChr
+                   , closeChr
+                   , openCount
+                   )
              end
 
-         fun fStart (strPos, str, _, absIdx, stl, _, {chr1, chr2}) =
-           loop (strPos, str, absIdx, stl, chr1, chr2)
+         fun fStart (strPos, str, _, absIdx, stl, _, {openChr, closeChr}) =
+           loop (strPos, str, absIdx, stl, openChr, closeChr, 0)
        end)
 
-  val toEitherChrNext = ToEitherChrNext.foldNext
+  val toCloseChrNext = ToCloseChrNext.foldNext
 
   structure NextPairChr =
     MakeIfCharFolderNext

fcore/normal-mode/make-normal-delete.sml

@@ -1035,6 +1035,51 @@ struct
       deleteAndFinish (app, low, length, buffer, time)
     end
 
+  fun deleteInsidePair (app: app_type, openChr, closeChr, time) =
+    let
+      val {buffer, cursorIdx, dfa, ...} = app
+
+      val buffer = LineGap.goToIdx (cursorIdx, buffer)
+      val nextIdx =
+        Cursor.toCloseChrNext
+          (buffer, cursorIdx, {openChr = openChr, closeChr = closeChr})
+    in
+      if nextIdx = ~1 then
+        NormalFinish.clearMode app
+      else
+        let
+          val buffer = LineGap.goToIdx (nextIdx, buffer)
+          val matchIdx = Cursor.matchPair (buffer, nextIdx)
+        in
+          if matchIdx = ~1 then
+            NormalFinish.clearMode app
+          else
+            let
+              val low = Int.min (nextIdx, matchIdx)
+              val high = Int.max (nextIdx, matchIdx)
+            in
+              if high = low + 1 then
+                NormalFinish.clearMode app
+              else
+                let
+                  val deleteLow = low + 1
+                  val length = high - deleteLow
+
+                  val buffer = LineGap.goToIdx (high, buffer)
+                  val initialMsg = Fn.initMsgs (deleteLow, length, buffer)
+
+                  val buffer = LineGap.delete (deleteLow, length, buffer)
+                  val (buffer, searchList) = SearchList.build (buffer, dfa)
+
+                  val buffer = LineGap.goToIdx (low, buffer)
+                in
+                  NormalFinish.buildTextAndClear
+                    (app, buffer, low, searchList, initialMsg, time)
+                end
+            end
+        end
+    end
+
   fun finishAfterDeleteInside (app: app_type, origLow, high, time) =
     if origLow = high then
       NormalFinish.clearMode app

fcore/normal-mode/normal-mode.sml

@@ -222,14 +222,18 @@ struct
       case chr of
         #"w" => NormalDelete.deleteInsideWord (app, time)
       | #"W" => NormalDelete.deleteInsideWORD (app, time)
-      | #"(" => NormalDelete.deleteInsideChrOpen (app, chr, time)
-      | #"[" => NormalDelete.deleteInsideChrOpen (app, chr, time)
-      | #"{" => NormalDelete.deleteInsideChrOpen (app, chr, time)
-      | #"<" => NormalDelete.deleteInsideChrOpen (app, chr, time)
-      | #")" => NormalDelete.deleteInsideChrClose (app, chr, time)
-      | #"]" => NormalDelete.deleteInsideChrClose (app, chr, time)
-      | #"}" => NormalDelete.deleteInsideChrClose (app, chr, time)
-      | #">" => NormalDelete.deleteInsideChrClose (app, chr, time)
+
+      | #"(" => NormalDelete.deleteInsidePair (app, #"(", #")", time)
+      | #")" => NormalDelete.deleteInsidePair (app, #"(", #")", time)
+
+      | #"[" => NormalDelete.deleteInsidePair (app, #"[", #"]", time)
+      | #"]" => NormalDelete.deleteInsidePair (app, #"[", #"]", time)
+
+      | #"{" => NormalDelete.deleteInsidePair (app, #"{", #"}", time)
+      | #"}" => NormalDelete.deleteInsidePair (app, #"{", #"}", time)
+
+      | #"<" => NormalDelete.deleteInsidePair (app, #"<", #">", time)
+      | #">" => NormalDelete.deleteInsidePair (app, #"<", #">", time)
       | _ => NormalFinish.clearMode app
 
     fun parseDeleteAround (app, chr, time) =

temp.txt

@@ -1 +1 @@
-(((hello)))
+( ( ( hello ) ) )