further refactoring, functorising a function because it will later be used elsewhere as well

fcore/cursor-dfa/make-dfa-loop.sml

@@ -61,3 +61,24 @@ struct
       | [] => cursorIdx
     end
 end
+
+functor MakePrevDfaLoopMinus1(M: MAKE_DFA_LOOP) =
+struct
+  fun prev (lineGap: LineGap.t, cursorIdx) =
+    let
+      val {idx = bufferIdx, leftStrings, ...} = lineGap
+      val strIdx = cursorIdx - bufferIdx - 1
+      val absIdx = cursorIdx - 1
+    in
+      if strIdx < 0 then
+        case leftStrings of
+          lhd :: ltl =>
+            M.fStart (String.size lhd - 1, absIdx, lhd, ltl, M.startState, 1)
+        | [] => 0
+      else
+        case #rightStrings lineGap of
+          rhd :: _ =>
+            M.fStart (strIdx, absIdx, rhd, leftStrings, M.startState, 1)
+        | [] => Int.max (0, cursorIdx - 2)
+    end
+end

fcore/cursor-dfa/vi-WORD-dfa.sml

@@ -108,14 +108,16 @@ struct
              end
        end)
 
-  val startOfNextWORD = StartOfNextWORD.next
+  structure StartOfCurrentWORD =
-  val endOfPrevWORD = EndOfPrevWORD.prev
+    MakePrevDfaLoopMinus1
+      (struct
+         val startState = startState
 
-  fun loopStartOfCurrentWORD (idx, absIdx, str, tl, currentState, counter) =
+         fun fStart (idx, absIdx, str, tl, currentState, counter) =
            if idx < 0 then
              case tl of
                str :: tl =>
-          loopStartOfCurrentWORD
+                 fStart
                    (String.size str - 1, absIdx, str, tl, currentState, counter)
              | [] => 0
            else
@@ -127,33 +129,14 @@ struct
                  if counter - 1 = 0 then
                    absIdx + 1
                  else
-            loopStartOfCurrentWORD
+                   fStart
                      (idx - 1, absIdx - 1, str, tl, startState, counter - 1)
                else
-          loopStartOfCurrentWORD
+                 fStart (idx - 1, absIdx - 1, str, tl, newState, counter)
-            (idx - 1, absIdx - 1, str, tl, newState, counter)
              end
+       end)
 
-  (* we do not rely on MakeDfaLoop functor because we want to 
+  val startOfNextWORD = StartOfNextWORD.next
-   * ignore the character the cursor is currently on,
+  val endOfPrevWORD = EndOfPrevWORD.prev
-   * and start tracking state from the character before the current one. *)
+  val startOfCurrentWORD = StartOfCurrentWORD.prev
-  fun startOfCurrentWORD (lineGap: LineGap.t, cursorIdx) =
-    let
-      val {idx = bufferIdx, leftStrings, ...} = lineGap
-      val strIdx = cursorIdx - bufferIdx - 1
-      val absIdx = cursorIdx - 1
-    in
-      if strIdx < 0 then
-        case leftStrings of
-          lhd :: ltl =>
-            loopStartOfCurrentWORD
-              (String.size lhd - 1, absIdx, lhd, ltl, startState, 1)
-        | [] => 0
-      else
-        case #rightStrings lineGap of
-          rhd :: _ =>
-            loopStartOfCurrentWORD
-              (strIdx, absIdx, rhd, leftStrings, startState, 1)
-        | [] => Int.max (0, cursorIdx - 2)
-    end
 end