make DFA for vi next WORD motion, still passing tests

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

@@ -0,0 +1,118 @@
+structure ViWORDDfa =
+struct
+  val startState = 0w0
+  val startNonBlankState = 0w1
+  val startSpaceState = 0w2
+  val nonBlankAfterSpaceState = 0w4
+
+  fun makeStart i =
+    let
+      val chr = Char.chr i
+    in
+      if Char.isSpace chr then
+        startSpaceState
+      else
+        startNonBlankState
+    end
+
+  fun makeStartNonBlankState i =
+    let
+      val chr = Char.chr i
+    in
+      if Char.isSpace chr then
+        startSpaceState
+      else
+        startNonBlankState
+    end
+
+  fun makeStartSpace i =
+    let
+      val chr = Char.chr i
+    in
+      if Char.isSpace chr then
+        startSpaceState
+      else
+        nonBlankAfterSpaceState
+    end
+
+  val startTable = Vector.tabulate (255, makeStart)
+  val startNonBlankTable = Vector.tabulate (255, makeStartNonBlankState)
+  val startSpaceTable = Vector.tabulate (255, makeStartSpace)
+
+  val tables = #[startTable, startNonBlankTable, startSpaceTable]
+
+  fun next (currentState, currentChar) =
+    let
+      val currentState = Word8.toInt currentState
+      val currentTable = Vector.sub (tables, currentState)
+      val charIdx = Char.ord currentChar
+    in
+      Vector.sub (currentTable, charIdx)
+    end
+
+  fun loopNextWORD (idx, absIdx, str, tl, currentState, counter) =
+    if idx = String.size str then
+      case tl of
+        str :: tl  =>
+          loopNextWORD (0, absIdx, str, tl, currentState, counter)
+      | [] =>
+          Int.max (absIdx - 2, 0)
+    else
+      let
+        val chr = String.sub (str, idx)
+        val newState = next (currentState, chr)
+      in
+        if newState = nonBlankAfterSpaceState then 
+          if counter = 0 then
+            absIdx
+          else
+            (* new loop, so reset to start state and proceed *)
+            loopNextWORD (idx + 1, absIdx + 1, str, tl, startState, counter - 1)
+        else
+          loopNextWORD (idx + 1, absIdx + 1, str, tl, newState, counter)
+      end
+
+  fun loopPrevWORD (idx, absIdx, str, tl, currentState, counter) =
+    if idx < 0 then
+      case tl of
+        str :: tl =>
+          loopPrevWORD (String.size str - 1, absIdx, str, tl, currentState, counter)
+      | [] => 0
+    else
+      let
+        val chr = String.sub (str, idx)
+        val newState = next (currentState, chr)
+      in
+        if newState = nonBlankAfterSpaceState then
+          if counter = 0 then
+            absIdx
+          else
+            (* reset to start state and proceed *)
+            loopPrevWORD (idx - 1, absIdx - 1, str, tl, startState, counter - 1)
+        else
+          loopPrevWORD (idx - 1, absIdx - 1, str, tl, newState, counter)
+      end
+
+  fun nextWORD (lineGap: LineGap.t, cursorIdx) =
+    let
+      val {rightStrings, idx = bufferIdx, ...} = lineGap
+    in
+      case rightStrings of
+        shd :: stl =>
+          let
+            (* convert absolute cursorIdx to idx relative to hd string *)
+            val strIdx = cursorIdx - bufferIdx
+          in
+            if strIdx < String.size shd then
+              (* strIdx is in this string *)
+              loopNextWORD (strIdx, cursorIdx, shd, stl, startState, 0)
+            else
+              (* strIdx is in tl *)
+              case stl of
+                 stlhd :: stltl =>
+                   loopNextWORD (strIdx, cursorIdx, stlhd, stltl, startState, 0)
+               | _ => cursorIdx
+          end
+      | [] => cursorIdx
+    end
+end

fcore/cursor.sml

@@ -886,8 +886,7 @@ struct
     toNextWord (lineGap, cursorIdx, helpNextWord)
 
   (* equivalent of vi's 'W' command *)
-  fun nextWORD (lineGap, cursorIdx) =
-    toNextWord (lineGap, cursorIdx, helpNextWORD)
+  val nextWORD = ViWORDDfa.nextWORD
 
   fun helpPrevWord (strPos, str, absIdx, strTl, lineTl) =
     if strPos < 0 then