From 8a5260ae50486c5e424d9778b7ec824b27842b9d Mon Sep 17 00:00:00 2001
From: Adam Scarr <adam@vektah.net>
Date: Mon, 11 Jun 2018 11:54:35 +1000
Subject: [PATCH] remove branch predictor in Any

fixes #2
---
 combinator.go      | 14 +-------------
 combinator_test.go | 45 ++++++++++++++++++---------------------------
 2 files changed, 19 insertions(+), 40 deletions(-)

diff --git a/combinator.go b/combinator.go
index 38145ee..5b0d584 100644
--- a/combinator.go
+++ b/combinator.go
@@ -36,7 +36,6 @@ func NoAutoWS(parser Parserish) Parser {
 func Any(parsers ...Parserish) Parser {
 	parserfied := ParsifyAll(parsers...)
 	// Records which parser was successful for each byte, and will use it first next time.
-	predictor := [255]int{}
 
 	return NewParser("Any()", func(ps *State, node *Result) {
 		ps.WS(ps)
@@ -45,13 +44,6 @@ func Any(parsers ...Parserish) Parser {
 			return
 		}
 		startpos := ps.Pos
-		predictorChar := ps.Input[startpos]
-		predicted := predictor[predictorChar]
-
-		parserfied[predicted](ps, node)
-		if !ps.Errored() {
-			return
-		}
 
 		longestError := ps.Error
 		if ps.Cut <= startpos {
@@ -60,10 +52,7 @@ func Any(parsers ...Parserish) Parser {
 			return
 		}
 
-		for i, parser := range parserfied {
-			if i == predicted {
-				continue
-			}
+		for _, parser := range parserfied {
 			parser(ps, node)
 			if ps.Errored() {
 				if ps.Error.pos >= longestError.pos {
@@ -75,7 +64,6 @@ func Any(parsers ...Parserish) Parser {
 				ps.Recover()
 				continue
 			}
-			predictor[predictorChar] = i
 			return
 		}
 
diff --git a/combinator_test.go b/combinator_test.go
index c1eedb3..aa16e21 100644
--- a/combinator_test.go
+++ b/combinator_test.go
@@ -4,6 +4,8 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+	"os"
+	"fmt"
 )
 
 func TestSeq(t *testing.T) {
@@ -62,38 +64,27 @@ func TestAny(t *testing.T) {
 		require.Equal(t, 0, p2.Pos)
 	})
 
-	t.Run("branch prediction", func(t *testing.T) {
-		p := Any("hello", Seq("{", Cut(), "world", "}"), Seq("[", Cut(), "a", "]"))
-		// warm up the predictor
-		_, _ = Run(p, "hello")
-		_, _ = Run(p, "{world}")
+	t.Run("overlapping longest match", func(t *testing.T) {
+		EnableLogging(os.Stdout)
+		p := Many(Any("ab", "a"))
 
-		t.Run("matches", func(t *testing.T) {
-			node, ps := runParser("hello world!", p)
-			require.Equal(t, "hello", node.Token)
-			require.Equal(t, 5, ps.Pos)
+		t.Run("a ab", func(t *testing.T) {
+			node, ps := runParser("a ab", p)
+
+			require.False(t, ps.Errored())
+			require.Equal(t, "a", node.Child[0].Token)
+			require.Equal(t, "ab", node.Child[1].Token)
 		})
 
-		t.Run("errors", func(t *testing.T) {
-			_, ps := runParser("help world!", p)
-			require.Equal(t, "offset 0: expected [", ps.Error.Error())
-			require.Equal(t, 0, ps.Error.Pos())
-			require.Equal(t, 0, ps.Pos)
-		})
+		t.Run("ab a", func(t *testing.T) {
+			node, ps := runParser("ab a", p)
 
-		t.Run("errors with cuts", func(t *testing.T) {
-			_, ps := runParser("{world", p)
-			require.Equal(t, "offset 6: expected }", ps.Error.Error())
-			require.Equal(t, 6, ps.Error.Pos())
-			require.Equal(t, 0, ps.Pos)
-		})
+			fmt.Println(node)
+
+			require.False(t, ps.Errored())
+			require.Equal(t, "ab", node.Child[0].Token)
+			require.Equal(t, "a", node.Child[1].Token)
 
-		t.Run("misprededicted cut", func(t *testing.T) {
-			// This should probably only happen when the predictor is cold
-			_, ps := runParser("[a", p)
-			require.Equal(t, "offset 2: expected ]", ps.Error.Error())
-			require.Equal(t, 2, ps.Error.Pos())
-			require.Equal(t, 0, ps.Pos)
 		})
 	})
 }