move if statement that only needs to be checked once from helpBinSearch, which is recursive, to binSearch which is not recursive, for negligibly better performance (fewer branch predictions)

src/line_gap.sml

@@ -49,7 +49,13 @@ struct
   val vecLimit = 32
 
   val empty =
-    {idx = 0, leftStrings = [], rightStrings = [], line = 0, leftLines = [], rightLines = []}
+    { idx = 0
+    , leftStrings = []
+    , rightStrings = []
+    , line = 0
+    , leftLines = []
+    , rightLines = []
+    }
 
   local
     fun helpToString (acc, input) =
@@ -71,9 +77,6 @@ struct
 
   local
     fun helpBinSearch (findNum, lines, low, high) =
-      if Vector.length lines = 0 then
-        0
-      else
       let
         val mid = low + ((high - low) div 2)
       in
@@ -93,7 +96,8 @@ struct
       end
   in
     fun binSearch (findNum, lines) =
-      helpBinSearch (findNum, lines, 0, Vector.length lines)
+      if Vector.length lines = 0 then 0
+      else helpBinSearch (findNum, lines, 0, Vector.length lines)
   end
 
   fun insWhenIdxAndCurIdxAreEqual
@@ -211,14 +215,17 @@ struct
         end
       else
         (* Just cons everything; no way we can join while staying in limit. *)
-        let val _ = print "line 210\n" in
+        let
+          val _ = print "line 210\n"
+        in
           { idx = curIdx + String.size newString
           , line = curLine + Vector.length newLines
           , leftStrings = leftStringsHd :: newString :: leftStringsTl
           , leftLines = leftLinesHd :: newLines :: leftLinesTl
           , rightStrings = rightStrings
           , rightLines = rightLines
-        } end
+          }
+        end
     else
       (* Need to insert in the middle of the left list. *)
       let
@@ -228,7 +235,8 @@ struct
         val strSub2 = String.substring
           (leftStringsHd, strLength, String.size leftStringsHd - strLength)
         val midpoint = binSearch (String.size strSub1, leftLinesHd)
-        val _ = print ("str size:" ^ Int.toString (Vector.length leftLinesHd) ^ "\n")
+        val _ = print
+          ("str size:" ^ Int.toString (Vector.length leftLinesHd) ^ "\n")
         val _ = print ("midpoint:" ^ Int.toString (midpoint) ^ "\n")
       in
         if
@@ -268,9 +276,9 @@ struct
            * staying in limit. *)
           let
             val _ = print "line 268\n"
-            val _ = print ("vector length: " ^ Int.toString (Vector.length newLines ) ^ "\n")
+            val _ = print
-            val _ = print ("midpoint: " ^ Int.toString (
+              ("vector length: " ^ Int.toString (Vector.length newLines) ^ "\n")
-            midpoint) ^ "\n")
+            val _ = print ("midpoint: " ^ Int.toString (midpoint) ^ "\n")
             val newLeftLines =
               Vector.tabulate (midpoint + Vector.length newLines, fn idx =>
                 if idx < midpoint then Vector.sub (leftLinesHd, idx)
@@ -505,14 +513,17 @@ struct
       else
         (* Cons newString and newLines to after-the-head,
          * because we can't join while staying in the limit.*)
-         let val _ = print "line 498\n" in
+        let
+          val _ = print "line 498\n"
+        in
           { idx = curIdx
           , line = curLine
           , leftStrings = leftStrings
           , leftLines = leftLines
           , rightStrings = rightStringsHd :: newString :: rightStringsTl
           , rightLines = rightLinesHd :: newLines :: rightLinesTl
-        } end
+          }
+        end
     else
       (* Have to split rightStringsHd and rightLinesHd in the middle. *)
       let
@@ -563,11 +574,8 @@ struct
             val newLeftStringsHd = strSub1 ^ newString
             val newLeftLinesHd =
               Vector.tabulate (Vector.length newLines + midpoint, fn idx =>
-                if idx < midpoint then 
+                if idx < midpoint then Vector.sub (rightLinesHd, idx)
-                  Vector.sub (rightLinesHd, idx)
+                else Vector.sub (newLines, accessIdx) + String.size strSub1)
-                else 
-                  Vector.sub (newLines, accessIdx) + String.size strSub1
-                  )
 
             val _ = print "line 584\n"
             val newRightLinesHd =
@@ -734,14 +742,17 @@ struct
         end
     | (_, _) =>
         (* Right string/line is empty. *)
-        let val _ = print "line 723\n" in
+        let
+          val _ = print "line 723\n"
+        in
           { idx = curIdx
           , line = curLine
           , leftStrings = leftStrings
           , leftLines = leftLines
           , rightStrings = [newString]
           , rightLines = [newLines]
-        } end
+          }
+        end
 
   fun ins
     ( idx