add two additional terminal yank operations: '<count-y-n> for copying to next match, and <count-y-N> for copying to prev match

fcore/normal-mode/normal-mode.sml

@@ -342,7 +342,50 @@ struct
               NormalModeWith.modeAndBuffer (app, buffer, mode, [DRAW msg])
             end
         end
-    (* todo: non-terminal chars, 'n' (go to next match) *)
+    | #"n" =>
+        let
+          open DrawMsg
+          open MailboxType
+
+          val {cursorIdx, searchList, buffer, ...} = app
+          val high = SearchList.nextMatch (cursorIdx, searchList, count)
+        in
+          if high = ~1 orelse high <= cursorIdx then
+            NormalFinish.clearMode app
+          else
+            let
+              val length = high - cursorIdx
+              val buffer = LineGap.goToIdx (high, buffer)
+
+              val str = LineGap.substring (cursorIdx, length, buffer)
+              val msg = YANK str
+              val mode = NORMAL_MODE ""
+            in
+              NormalModeWith.modeAndBuffer (app, buffer, mode, [DRAW msg])
+            end
+        end
+    | #"N" =>
+        let
+          open DrawMsg
+          open MailboxType
+
+          val {cursorIdx, searchList, buffer, ...} = app
+          val low = SearchList.prevMatch (cursorIdx, searchList, count)
+        in
+          if low = ~1 orelse low >= cursorIdx then
+            NormalFinish.clearMode app
+          else
+            let
+              val length = cursorIdx - low
+
+              val str = LineGap.substring (low, length, buffer)
+              val msg = YANK str
+              val mode = NORMAL_MODE ""
+            in
+              NormalModeWith.modeAndBuffer (app, buffer, mode, [DRAW msg])
+            end
+        end
+    (* todo: non-terminal chars *)
     | _ => NormalFinish.clearMode app
 
   fun parseYank (strPos, str, count, app, chrCmd, time) =