Apostrophes are serious business

.gitea/workflows/pr.yaml

@@ -0,0 +1,18 @@
+name: Test and check
+on:
+  - push
+jobs:
+  test-and-check:
+    runs-on: brandon-ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/setup-go@v7
+        with:
+          go-version-file: go.mod
+          cache-dependency-path: go.sum
+      - name: Check SPDX headers
+        run: go run ./internal/check
+      - name: Run unit tests
+        run: go test ./...
+
+

README.md

@@ -1,8 +1,8 @@
 # Gigaparsec
 
 [![Go Reference](https://pkg.go.dev/badge/git.codemonkeysoftware.net/b/gigaparsec.svg)](https://pkg.go.dev/git.codemonkeysoftware.net/b/gigaparsec)
-![Total garbage.](https://img.shields.io/badge/Total-garbage-red)
+
+by Brandon Dyck <[brandon@dyck.us](mailto:brandon@dyck.us)>
 
 Monadic parser combinators in Go
 
-**I don't recommend using this yet. It is very unfinished and it will break.**

TODO.txt

@@ -1,6 +1,3 @@
-Write Repeat tests
-Think about not requiring so much Pos() when making messages
-Rename Seq2 to Seq
-Document Seq
-Should MakeState be private now that there's Run?
-What's Megaparsec got that we ain't got?
+Think about changing "consume" to "commit"
+What’s Megaparsec got that we ain’t got?
+chainl

bind.go

@@ -4,7 +4,7 @@
 
 package gigaparsec
 
-// Bind combines p with a parser created by f that depends on p's result value.
+// Bind combines p with a parser created by f that depends on p’s result value.
 func Bind[In, Out, T any](
 	p Parser[In, T],
 	f func(T) Parser[In, Out],
@@ -33,7 +33,7 @@ func Bind[In, Out, T any](
 			return Fail[In, Out](anyConsumed, r2.Message()), nil
 		}
 
-		return Succeed(anyConsumed, val2, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, val2, next, s.MessageOK()), nil
 	}
 }
 
@@ -77,7 +77,7 @@ func Bind2[In, Out, T, T2 any](
 			return Fail[In, Out](anyConsumed, r3.Message()), nil
 		}
 
-		return Succeed(anyConsumed, val3, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, val3, next, s.MessageOK()), nil
 	}
 }
 
@@ -132,7 +132,7 @@ func Bind3[In, Out, T, T2, T3 any](
 			return Fail[In, Out](anyConsumed, r4.Message()), nil
 		}
 
-		return Succeed(anyConsumed, val4, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, val4, next, s.MessageOK()), nil
 	}
 }
 
@@ -198,7 +198,7 @@ func Bind4[In, Out, T, T2, T3, T4 any](
 			return Fail[In, Out](anyConsumed, r5.Message()), nil
 		}
 
-		return Succeed(anyConsumed, val5, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, val5, next, s.MessageOK()), nil
 	}
 }
 
@@ -275,6 +275,424 @@ func Bind5[In, Out, T, T2, T3, T4, T5 any](
 			return Fail[In, Out](anyConsumed, r6.Message()), nil
 		}
 
-		return Succeed(anyConsumed, val6, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, val6, next, s.MessageOK()), nil
+	}
+}
+
+// Bind6 is equivalent to 6 nested calls to Bind.
+func Bind6[In, Out, T, T2, T3, T4, T5, T6 any](
+	p Parser[In, T],
+	f func(T) Parser[In, T2],
+	f2 func(T2) Parser[In, T3],
+	f3 func(T3) Parser[In, T4],
+	f4 func(T4) Parser[In, T5],
+	f5 func(T5) Parser[In, T6],
+	f6 func(T6) Parser[In, Out],
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := f(val)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := f2(val2)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := f3(val3)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := f4(val4)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := f5(val5)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		r7, err := f6(val6)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r7.Consumed()
+		success, val7, next := r7.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r7.Message()), nil
+		}
+
+		return Succeed(anyConsumed, val7, next, s.MessageOK()), nil
+	}
+}
+
+// Bind7 is equivalent to 7 nested calls to Bind.
+func Bind7[In, Out, T, T2, T3, T4, T5, T6, T7 any](
+	p Parser[In, T],
+	f func(T) Parser[In, T2],
+	f2 func(T2) Parser[In, T3],
+	f3 func(T3) Parser[In, T4],
+	f4 func(T4) Parser[In, T5],
+	f5 func(T5) Parser[In, T6],
+	f6 func(T6) Parser[In, T7],
+	f7 func(T7) Parser[In, Out],
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := f(val)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := f2(val2)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := f3(val3)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := f4(val4)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := f5(val5)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		r7, err := f6(val6)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r7.Consumed()
+		success, val7, next := r7.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r7.Message()), nil
+		}
+
+		r8, err := f7(val7)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r8.Consumed()
+		success, val8, next := r8.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r8.Message()), nil
+		}
+
+		return Succeed(anyConsumed, val8, next, s.MessageOK()), nil
+	}
+}
+
+// Bind8 is equivalent to 8 nested calls to Bind.
+func Bind8[In, Out, T, T2, T3, T4, T5, T6, T7, T8 any](
+	p Parser[In, T],
+	f func(T) Parser[In, T2],
+	f2 func(T2) Parser[In, T3],
+	f3 func(T3) Parser[In, T4],
+	f4 func(T4) Parser[In, T5],
+	f5 func(T5) Parser[In, T6],
+	f6 func(T6) Parser[In, T7],
+	f7 func(T7) Parser[In, T8],
+	f8 func(T8) Parser[In, Out],
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := f(val)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := f2(val2)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := f3(val3)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := f4(val4)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := f5(val5)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		r7, err := f6(val6)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r7.Consumed()
+		success, val7, next := r7.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r7.Message()), nil
+		}
+
+		r8, err := f7(val7)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r8.Consumed()
+		success, val8, next := r8.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r8.Message()), nil
+		}
+
+		r9, err := f8(val8)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r9.Consumed()
+		success, val9, next := r9.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r9.Message()), nil
+		}
+
+		return Succeed(anyConsumed, val9, next, s.MessageOK()), nil
+	}
+}
+
+// Bind9 is equivalent to 9 nested calls to Bind.
+func Bind9[In, Out, T, T2, T3, T4, T5, T6, T7, T8, T9 any](
+	p Parser[In, T],
+	f func(T) Parser[In, T2],
+	f2 func(T2) Parser[In, T3],
+	f3 func(T3) Parser[In, T4],
+	f4 func(T4) Parser[In, T5],
+	f5 func(T5) Parser[In, T6],
+	f6 func(T6) Parser[In, T7],
+	f7 func(T7) Parser[In, T8],
+	f8 func(T8) Parser[In, T9],
+	f9 func(T9) Parser[In, Out],
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := f(val)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := f2(val2)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := f3(val3)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := f4(val4)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := f5(val5)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		r7, err := f6(val6)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r7.Consumed()
+		success, val7, next := r7.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r7.Message()), nil
+		}
+
+		r8, err := f7(val7)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r8.Consumed()
+		success, val8, next := r8.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r8.Message()), nil
+		}
+
+		r9, err := f8(val8)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r9.Consumed()
+		success, val9, next := r9.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r9.Message()), nil
+		}
+
+		r10, err := f9(val9)(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r10.Consumed()
+		success, val10, next := r10.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r10.Message()), nil
+		}
+
+		return Succeed(anyConsumed, val10, next, s.MessageOK()), nil
 	}
 }

bytes/bytes.go

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: Unlicense
+
+package bytes
+
+import (
+	"git.codemonkeysoftware.net/b/gigaparsec"
+)
+
+// Token wraps a parser to discard all whitespace after the parsed input.
+// whitespace is a parser that will consume non-empty whitespace.
+func Token[Out any](whitespace gigaparsec.Parser[byte, struct{}]) func(p gigaparsec.Parser[byte, Out]) gigaparsec.Parser[byte, Out] {
+	mappedWS := whitespace.Map(func(struct{}) struct{} { return struct{}{} })
+	var ignoreWS gigaparsec.Parser[byte, struct{}] = func(s gigaparsec.State[byte]) (gigaparsec.Result[byte, struct{}], error) {
+		result, err := mappedWS(s)
+		return result.Consume(false), err
+	}
+	return func(p gigaparsec.Parser[byte, Out]) gigaparsec.Parser[byte, Out] {
+		return gigaparsec.Seq(p, gigaparsec.Repeat(0, ignoreWS), func(val Out, _ []struct{}) Out { return val })
+	}
+}
+
+func isWhitespaceASCII(b byte) bool {
+	return b == ' ' || (b >= '\t' && b <= '\r')
+}
+
+// WhitespaceASCII consumes one ASCII whitespace character: space, tab, LF, CR, vertical tab, or form feed.
+func WhitespaceASCII() gigaparsec.Parser[byte, struct{}] {
+	return gigaparsec.Satisfy(isWhitespaceASCII).Map(func(byte) struct{} { return struct{}{} })
+}

bytes/bytes_test.go

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: Unlicense
+
+package bytes_test
+
+import (
+	"fmt"
+	"strings"
+
+	"git.codemonkeysoftware.net/b/gigaparsec"
+	"git.codemonkeysoftware.net/b/gigaparsec/bytes"
+)
+
+func Example() {
+	ptokens := gigaparsec.Choose(
+		bytes.MatchString("("),
+		bytes.MatchString(")"),
+		bytes.MatchString("+"),
+		bytes.MatchString("-"),
+		bytes.Regexp(`[a-zA-Z][a-zA-Z0-9_]*`).Label("identifier"),
+		bytes.Regexp(`[0-9]+`).Label("number"),
+	)
+
+	tokenize := gigaparsec.Repeat(0, bytes.Token[string](bytes.WhitespaceASCII())(ptokens))
+	const src = `(alpha
+		 + 42  ) -5  `
+	tokens, _ := tokenize.Run(strings.NewReader(src))
+	for _, token := range tokens {
+		fmt.Println(token)
+	}
+
+	// Output:
+	// (
+	// alpha
+	// +
+	// 42
+	// )
+	// -
+	// 5
+}

bytes/regexp.go

@@ -69,22 +69,25 @@ func Regexp(pattern string) gigaparsec.Parser[byte, string] {
 			return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: reader error: %w", err)
 		}
 		if idx == nil {
+			if err == io.EOF {
+				return gigaparsec.Fail[byte, string](false, input.MessageOK()), nil
+			}
 			got := make([]byte, r.Count())
 			_, _, err = input.Read(got)
 			if err != nil {
 				return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: unexpected error: %w", err)
 			}
-			return gigaparsec.Fail[byte, string](false, gigaparsec.MakeMessage(input.Pos(), string(got), expected)), nil
+			return gigaparsec.Fail[byte, string](false, input.Message(string(got), expected)), nil
 		}
 		// Alas, this is a little wasteful because a Regexp can only return indices
 		// when searching a RuneReader.
 		dst := make([]byte, idx[1]-idx[0])
 		n, _, err := input.Read(dst)
-		if err != nil {
+		if err != nil && (!errors.Is(err, io.EOF) || n < uint64(len(dst))) {
 			return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: unexpected error: %w", err)
 		}
 		next := input.At(input.Pos() + n)
-		return gigaparsec.Succeed(true, string(dst), next, gigaparsec.MessageOK(input.Pos())), nil
+		return gigaparsec.Succeed(true, string(dst), next, input.MessageOK()), nil
 	}
 }
 
@@ -95,14 +98,14 @@ func MatchString(s string) gigaparsec.Parser[byte, string] {
 		dst := make([]byte, len(s))
 		_, next, err := input.Read(dst)
 		if errors.Is(err, io.EOF) {
-			return gigaparsec.Fail[byte, string](false, gigaparsec.MessageEnd(input.Pos(), expected)), nil
+			return gigaparsec.Fail[byte, string](false, input.MessageEnd(expected)), nil
 		}
 		if err != nil {
 			return gigaparsec.Result[byte, string]{}, fmt.Errorf("MatchString: %w", err)
 		}
 		if !bytes.Equal(dst, b) {
-			return gigaparsec.Fail[byte, string](false, gigaparsec.MakeMessage(input.Pos(), string(dst), expected)), nil
+			return gigaparsec.Fail[byte, string](false, input.Message(string(dst), expected)), nil
 		}
-		return gigaparsec.Succeed(true, s, next, gigaparsec.MessageOK(input.Pos())), nil
+		return gigaparsec.Succeed(true, s, next, input.MessageOK()), nil
 	}
 }

bytes/regexp_test.go

@@ -4,6 +4,7 @@ package bytes_test
 
 import (
 	"bytes"
+	"errors"
 	"strings"
 	"testing"
 
@@ -16,24 +17,64 @@ import (
 	"pgregory.net/rapid"
 )
 
-func Todo(t *testing.T) {
-	t.Fatalf("TODO")
-}
-
 func TestRegexp(t *testing.T) {
-	t.Run("only searches the beginning of input", Todo)
-	t.Run("position is correct after match", Todo)
-	t.Run("fails on unexpected error", Todo)
-	t.Run("returns a useful Got value", rapid.MakeCheck(func(t *rapid.T) {
+	alpha := rapid.SliceOfBytesMatching(`[A-Za-z]{1,100}`)
+	t.Run("position and value are correct after match", rapid.MakeCheck(func(t *rapid.T) {
+		needle := alpha.Draw(t, "needle")
+		input := rapid.Map(alpha, func(suffix []byte) []byte { return append(needle, suffix...) }).
+			Draw(t, "input")
+
+		p := pbytes.Regexp(string(needle))
+		result, err := p.RunToResult(bytes.NewReader(input))
+		succeeded, val, next := result.Status()
 
-	}))
-	t.Run("basically works", func(t *testing.T) {
-		result, err := pbytes.Regexp("a")(gigaparsec.MakeState(strings.NewReader("a")))
 		must.NoError(t, err)
-		success, value, _ := result.Status()
-		test.True(t, success, test.Sprint(result.Message()))
-		test.EqOp(t, "a", value)
-		test.True(t, result.Consumed())
+		test.True(t, succeeded)
+		test.EqOp(t, string(needle), val)
+		ptest.StateIsAt(t, next, uint64(len(needle)))
+	}))
+	t.Run("only searches the beginning of input", rapid.MakeCheck(func(t *rapid.T) {
+		needle := alpha.Draw(t, "needle")
+		input := rapid.Map(alpha, func(prefix []byte) []byte { return append(prefix, needle...) }).
+			Filter(func(b []byte) bool { return !bytes.HasPrefix(b, needle) }).
+			Draw(t, "input")
+
+		p := pbytes.Regexp(string(needle))
+		result, err := p.RunToResult(bytes.NewReader(input))
+		succeeded, _, _ := result.Status()
+
+		must.NoError(t, err)
+		test.False(t, succeeded)
+	}))
+	t.Run("fails on unexpected error", func(t *testing.T) {
+		expectedErr := errors.New("it broke")
+		p := pbytes.Regexp("nope")
+		result, err := p.RunToResult(ptest.ErrReaderAt(expectedErr))
+		succeeded, _, _ := result.Status()
+		test.ErrorIs(t, err, expectedErr)
+		test.False(t, succeeded)
+	})
+	t.Run("returns a useful Got value", func(t *testing.T) {
+		p := pbytes.Regexp("hello")
+		result, err := p.RunToResult(strings.NewReader("hellaparsec"))
+
+		must.NoError(t, err)
+		test.StrContains(t, result.Message().Got(), "hella")
+	})
+	t.Run("succeeds on empty matches", func(t *testing.T) {
+		p := pbytes.Regexp(".*")
+		result, err := p.RunToResult(strings.NewReader(""))
+		succeeded, value, _ := result.Status()
+		must.NoError(t, err)
+		must.True(t, succeeded)
+		must.EqOp(t, "", value)
+	})
+	t.Run("fails without an error at EOF", func(t *testing.T) {
+		p := pbytes.Regexp("a")
+		result, err := p.RunToResult(strings.NewReader(""))
+		succeeded, _, _ := result.Status()
+		must.NoError(t, err)
+		must.False(t, succeeded)
 	})
 }
 

gigaparsec.go

@@ -2,7 +2,7 @@
 
 package gigaparsec
 
-//go:generate go run ./internal/bindgen -bindpath bind.go -seqpath seq.go -max 5 -pkg gigaparsec
+//go:generate go run ./internal/bindgen -bindpath bind.go -seqpath seq.go -max 9 -pkg gigaparsec
 import (
 	"errors"
 	"fmt"
@@ -59,12 +59,24 @@ func (r Result[In, Out]) Message() Message {
 	return r.message
 }
 
-func MakeMessage(pos uint64, got string, expected ...string) Message {
-	return Message{
-		pos:      pos,
-		got:      got,
-		expected: expected,
+type ReaderAt[T any] interface {
+	ReadAt(p []T, off int64) (n int, err error)
+}
+
+type SliceReaderAt[T any] []T
+
+func (s SliceReaderAt[T]) ReadAt(dst []T, off int64) (n int, err error) {
+	if off < 0 {
+		return 0, errors.New("SliceReaderAt.ReadAt: negative offset")
 	}
+	if off >= int64(len(s)) {
+		return 0, io.EOF
+	}
+	n = copy(dst, s[off:])
+	if n < len(dst) {
+		err = io.EOF
+	}
+	return n, err
 }
 
 type Message struct {
@@ -107,47 +119,38 @@ func (m Message) String() string {
 	return s
 }
 
+func MakeMessage(pos uint64, got string, expected ...string) Message {
+	return Message{
+		pos:      pos,
+		got:      got,
+		expected: expected,
+	}
+}
+
 func MessageOK(pos uint64) Message { return Message{pos: pos} }
 
 func MessageEnd(pos uint64, expected ...string) Message {
 	return Message{pos: pos, got: "end of input", expected: expected}
 }
 
-type ReaderAt[T any] interface {
-	ReadAt(p []T, off int64) (n int, err error)
-}
-
-type SliceReaderAt[T any] []T
-
-func (s SliceReaderAt[T]) ReadAt(dst []T, off int64) (n int, err error) {
-	if off < 0 {
-		return 0, errors.New("SliceReaderAt.ReadAt: negative offset")
-	}
-	if off >= int64(len(s)) {
-		return 0, io.EOF
-	}
-	n = copy(dst, s[off:])
-	if n < len(dst) {
-		err = io.EOF
-	}
-	return n, err
-}
-
+// MakeState creates a new State.
+// It’s mostly useful for testing. You probably don’t need it.
 func MakeState[In any](r ReaderAt[In]) State[In] {
 	return State[In]{r: r}
 }
 
+// State represents a position in an input source.
 type State[In any] struct {
 	r   ReaderAt[In]
 	pos uint64
 }
 
-// Read fills dst with data from this State's position in the underlying source.
+// Read fills dst with data from this State’s position in the underlying source.
 // It returns the number of data it read and a new State for the position at which
 // the read ended, and an error if the read either (1) failed or (2) reached the
 // end of the source before filling dst. All reads from a given State will return
 // data from the same position the source.
-// If the source had too few data left to fill dst, or if the State's position is
+// If the source had too few data left to fill dst, or if the State’s position is
 // at or past the end of the source, err will be io.EOF.
 func (s State[In]) Read(dst []In) (n uint64, next State[In], err error) {
 	if s.pos > math.MaxInt64 {
@@ -166,7 +169,7 @@ func (s State[In]) Read(dst []In) (n uint64, next State[In], err error) {
 	return uint64(nread), s, err
 }
 
-// Pos returns this State's position.
+// Pos returns this State’s position.
 func (s State[In]) Pos() uint64 {
 	return s.pos
 }
@@ -176,6 +179,16 @@ func (s State[In]) At(pos uint64) State[In] {
 	return State[In]{r: s.r, pos: pos}
 }
 
+func (s State[In]) Message(got string, expected ...string) Message {
+	return MakeMessage(s.pos, got, expected...)
+}
+
+func (s State[In]) MessageOK() Message { return MessageOK(s.pos) }
+
+func (s State[in]) MessageEnd(expected ...string) Message {
+	return MessageEnd(s.pos, expected...)
+}
+
 type Parser[In, Out any] func(State[In]) (Result[In, Out], error)
 
 // Label creates a parser identical to p, except that a failed result will
@@ -194,15 +207,34 @@ func (p Parser[In, Out]) Label(label string) Parser[In, Out] {
 	}
 }
 
-type ParseError Message
-
-func (pe ParseError) Error() string {
-	return Message(pe).String()
+// Where creates a parser that fails if pred does not hold.
+func (p Parser[In, Out]) Where(pred func(Out) bool) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		result, err := p(s)
+		if result.success && !pred(result.value) {
+			result.success = false
+			result.message.got = "failed Where predicate"
+		}
+		return result, err
+	}
 }
 
-func Run[In, Out any](p Parser[In, Out], r ReaderAt[In]) (out Out, err error) {
+// Map creates a parser that converts the output of p from Out1 to Out2.
+func (p Parser[In, Out]) Map[Out2 any](f func(Out) Out2) Parser[In, Out2] {
+	return Bind(p, func(out Out) Parser[In, Out2] {
+		return Return[In](f(out))
+	})
+}
+
+// RunToResult executes a parser on r and returns the result, or an error if reading the inputs fails.
+func (p Parser[In, Out]) RunToResult(r ReaderAt[In]) (Result[In, Out], error) {
 	start := MakeState(r)
-	result, err := p(start)
+	return p(start)
+}
+
+// Run executes a parser on r and returns the output, or an an error if the parse fails.
+func (p Parser[In, Out]) Run(r ReaderAt[In]) (out Out, err error) {
+	result, err := p.RunToResult(r)
 	if err != nil {
 		err = fmt.Errorf("Run: %w", err)
 		return
@@ -215,10 +247,16 @@ func Run[In, Out any](p Parser[In, Out], r ReaderAt[In]) (out Out, err error) {
 	return
 }
 
+type ParseError Message
+
+func (pe ParseError) Error() string {
+	return Message(pe).String()
+}
+
 // Return creates a parser that always succeeds and returns value without consuming any input.
 func Return[In, Out any](value Out) Parser[In, Out] {
 	return func(state State[In]) (Result[In, Out], error) {
-		return Succeed(false, value, state, MessageOK(state.Pos())), nil
+		return Succeed(false, value, state, state.MessageOK()), nil
 	}
 }
 
@@ -229,7 +267,7 @@ func Satisfy[T any](pred func(T) bool) Parser[T, T] {
 		token := make([]T, 1)
 		n, next, err := state.Read(token)
 		if errors.Is(err, io.EOF) {
-			return Fail[T, T](false, MessageEnd(state.Pos())), nil
+			return Fail[T, T](false, state.MessageEnd()), nil
 		}
 		if err != nil {
 			return Result[T, T]{}, err
@@ -238,9 +276,9 @@ func Satisfy[T any](pred func(T) bool) Parser[T, T] {
 			panic(fmt.Sprintf("expected 1 element from Read, but got %d", n))
 		}
 		if pred(token[0]) {
-			return Succeed(true, token[0], next, MessageOK(state.Pos())), nil
+			return Succeed(true, token[0], next, state.MessageOK()), nil
 		}
-		return Fail[T, T](false, MakeMessage(state.Pos(), fmt.Sprint(token))), nil
+		return Fail[T, T](false, state.Message(fmt.Sprint(token))), nil
 	}
 }
 
@@ -252,15 +290,15 @@ func Match[T comparable](x T) Parser[T, T] {
 		token := make([]T, 1)
 		_, next, err := state.Read(token)
 		if errors.Is(err, io.EOF) {
-			return Fail[T, T](false, MessageEnd(state.Pos())), nil
+			return Fail[T, T](false, state.MessageEnd()), nil
 		}
 		if err != nil {
 			return Result[T, T]{}, err
 		}
 		if token[0] == x {
-			return Succeed(true, token[0], next, MessageOK(state.Pos())), nil
+			return Succeed(true, token[0], next, state.MessageOK()), nil
 		}
-		return Fail[T, T](false, MakeMessage(state.Pos(), fmt.Sprint(token), expected)), nil
+		return Fail[T, T](false, state.Message(fmt.Sprint(token), expected)), nil
 	}
 }
 
@@ -272,15 +310,15 @@ func MatchSlice[T comparable](s []T) Parser[T, []T] {
 		token := make([]T, len(s))
 		_, next, err := state.Read(token)
 		if errors.Is(err, io.EOF) {
-			return Fail[T, []T](false, MessageEnd(state.Pos())), nil
+			return Fail[T, []T](false, state.MessageEnd()), nil
 		}
 		if err != nil {
 			return Result[T, []T]{}, err
 		}
 		if !slices.Equal(s, token) {
-			return Fail[T, []T](false, MakeMessage(state.Pos(), fmt.Sprint(token), expected)), nil
+			return Fail[T, []T](false, state.Message(fmt.Sprint(token), expected)), nil
 		}
-		return Succeed(true, token, next, MessageOK(state.Pos())), nil
+		return Succeed(true, token, next, state.MessageOK()), nil
 	}
 }
 
@@ -317,7 +355,7 @@ func Choose[In, Out any](p Parser[In, Out], ps ...Parser[In, Out]) Parser[In, Ou
 				got = qMsg.got
 			}
 		}
-		msg := MakeMessage(input.Pos(), got, slices.Concat(expecteds...)...)
+		msg := input.Message(got, slices.Concat(expecteds...)...)
 		if failed {
 			return Fail[In, Out](false, msg), nil
 		}
@@ -344,22 +382,15 @@ func Try[In, Out any](p Parser[In, Out]) Parser[In, Out] {
 	}
 }
 
-// Map creates a parser that converts the output of p from Out1 to Out2.
-func Map[In, Out1, Out2 any](p Parser[In, Out1], f func(Out1) Out2) Parser[In, Out2] {
-	return Bind(p, func(out Out1) Parser[In, Out2] {
-		return Return[In](f(out))
-	})
-}
-
 func end[In any](s State[In]) (Result[In, struct{}], error) {
 	_, _, err := s.Read([]In{})
 	if errors.Is(err, io.EOF) {
-		return Succeed(true, struct{}{}, s, MessageOK(s.Pos())), nil
+		return Succeed(true, struct{}{}, s, s.MessageOK()), nil
 	}
 	if err != nil {
 		return Result[In, struct{}]{}, fmt.Errorf("End: unexpected error: %w", err)
 	}
-	return Fail[In, struct{}](false, MakeMessage(s.Pos(), "", "end of input")), nil
+	return Fail[In, struct{}](false, s.Message("", "end of input")), nil
 }
 
 // End creates a parser that succeeds at the end of the input and fails otherwise.
@@ -379,26 +410,41 @@ func Pipe[In, Ignore, Through any](p Parser[In, Ignore]) func(Through) Parser[In
 // It succeeds if and only if p succeeds at least minCount times.
 // It consumes if and only if at least one of the applications of p consumes.
 func Repeat[In, Out any](minCount int, p Parser[In, Out]) Parser[In, []Out] {
-	return func(s State[In]) (Result[In, []Out], error) {
+	return func(state State[In]) (Result[In, []Out], error) {
 		var values []Out
 		var consumed bool
-		next := s
+		currState := state
 		for {
-			result, err := p(next)
+			result, err := p(currState)
 			if err != nil {
 				return Result[In, []Out]{}, fmt.Errorf("AtLeastN: %w", err)
 			}
 			consumed = consumed || result.Consumed()
 			var value Out
 			var success bool
-			success, value, next = result.Status()
+			success, value, nextState := result.Status()
 			if !success {
 				if len(values) >= minCount {
-					return Succeed(consumed, values, next, MessageOK(s.Pos())), nil
+					return Succeed(consumed, values, currState, state.MessageOK()), nil
 				}
 				return Fail[In, []Out](consumed, result.Message()), nil
 			}
+			currState = nextState
 			values = append(values, value)
 		}
 	}
 }
+
+// Lazy delays creating a parser from p until the parser is called.
+// This is useful for preventing recursive function calls in the
+// definition of a recursive parser.
+func Lazy[In, Out any](p func() Parser[In, Out]) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		return p()(s)
+	}
+}
+
+// Bracket parses p, flanked by left and right.
+func Bracket[In, Out, LOut, ROut any](left Parser[In, LOut], p Parser[In, Out], right Parser[In, ROut]) Parser[In, Out] {
+	return Seq3(left, p, right, func(_ LOut, val Out, _ ROut) Out { return val })
+}

go.mod

@@ -1,6 +1,6 @@
 module git.codemonkeysoftware.net/b/gigaparsec
 
-go 1.23
+go 1.27
 
 require (
 	github.com/shoenig/test v1.11.0

inspiration.md

@@ -1,19 +1,19 @@
 - Hutton & Meijer, _[Monadic Parser Combinators](http://www.cs.nott.ac.uk/~pszgmh/monparsing.pdf)_
 
-The original paper on monadic parser combinators.
+  The original paper on monadic parser combinators.
 
 - Leijen & Meijer, _[Parsec: Direct Style Monadic Parser Combinators For The Real World](https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/parsec-paper-letter.pdf)_
 
-Describes Parsec, a monadic parser combinator library that limits backtracking by default and adds better error messages.
+  Describes Parsec, a monadic parser combinator library that limits backtracking by default and adds better error messages.
 
 - [Megaparsec](https://hackage.haskell.org/package/megaparsec)
 
-Improved fork of Megaparsec.
+  Improved fork of Megaparsec.
 
 - [FParsec](https://github.com/stephan-tolksdorf/fparsec)
 
-Parsec implementation in F#.
+  Parsec implementation in F#.
 
 - [Sprache](https://github.com/sprache/Sprache)
 
-Parsec implementation in C#.
+  Parsec implementation in C#.

internal/bindgen/bind.go.tmpl

@@ -5,7 +5,7 @@
 {{end}}{{end}}{{end -}}
 
 {{define "func" -}}
-{{if eq . 1}}// Bind combines p with a parser created by f that depends on p's result value.
+{{if eq . 1}}// Bind combines p with a parser created by f that depends on p’s result value.
 {{- else}}// Bind{{.}} is equivalent to {{.}} nested calls to Bind.{{end}}
 func Bind{{.}}[In, Out{{range .Count}}, T{{.}}{{end}} any](
 	p Parser[In, T],
@@ -24,7 +24,7 @@ func Bind{{.}}[In, Out{{range .Count}}, T{{.}}{{end}} any](
 			return Fail[In, Out](anyConsumed, r{{.}}.Message()), nil
 		}
 {{end}}
-		return Succeed(anyConsumed, val{{.Next}}, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, val{{.Next}}, next, s.MessageOK()), nil
 	}
 }{{end -}}
 

internal/bindgen/seq.go.tmpl

@@ -1,7 +1,8 @@
 {{/* SPDX-License-Identifier: Unlicense */ -}}
 
 {{define "func"}}{{if gt . 1 -}}
-func Seq{{.}}[In, Out{{range .Count}}, T{{.}}{{end}} any](
+// Seq{{if gt . 2}}{{.}}{{end}} runs {{.}} parsers in sequence and maps their collected results with f.
+func Seq{{if gt . 2}}{{.}}{{end}}[In, Out{{range .Count}}, T{{.}}{{end}} any](
 	{{- range .Count}}
 	p{{.}} Parser[In, T{{.}}],{{end}}
 	f func({{range .Count}}{{if ne . 1}}, {{end}}T{{.}}{{end}}) Out,
@@ -21,7 +22,7 @@ func Seq{{.}}[In, Out{{range .Count}}, T{{.}}{{end}} any](
 		}
 {{end}}
 		final := f({{range .Count}}{{if ne . 1}}, {{end}}val{{.}}{{end}})
-		return Succeed(anyConsumed, final, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
 	}
 }{{end}}{{end -}}
 

naive/naive.go

@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: Unlicense
+
+// Package naive contains naïve implementations of the Bind and Seq combinators.
+// The accompanying tests include simple benchmarks comparing their performance.
+package naive
+
+import gp "git.codemonkeysoftware.net/b/gigaparsec"
+
+func Bind2[In, Out, T, T2 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(p, f), f2)
+}
+func Bind3[In, Out, T, T2, T3, T4, T5, T6, T7, T8, T9 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, T3],
+	f3 func(T3) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(gp.Bind(p, f), f2), f3)
+}
+func Bind4[In, Out, T, T2, T3, T4 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, T3],
+	f3 func(T3) gp.Parser[In, T4],
+	f4 func(T4) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(gp.Bind(gp.Bind(p, f), f2), f3), f4)
+}
+func Bind5[In, Out, T, T2, T3, T4, T5 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, T3],
+	f3 func(T3) gp.Parser[In, T4],
+	f4 func(T4) gp.Parser[In, T5],
+	f5 func(T5) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(p, f), f2), f3), f4), f5)
+}
+func Bind6[In, Out, T, T2, T3, T4, T5, T6 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, T3],
+	f3 func(T3) gp.Parser[In, T4],
+	f4 func(T4) gp.Parser[In, T5],
+	f5 func(T5) gp.Parser[In, T6],
+	f6 func(T6) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(p, f), f2), f3), f4), f5), f6)
+}
+func Bind7[In, Out, T, T2, T3, T4, T5, T6, T7 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, T3],
+	f3 func(T3) gp.Parser[In, T4],
+	f4 func(T4) gp.Parser[In, T5],
+	f5 func(T5) gp.Parser[In, T6],
+	f6 func(T6) gp.Parser[In, T7],
+	f7 func(T7) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(p, f), f2), f3), f4), f5), f6), f7)
+}
+func Bind8[In, Out, T, T2, T3, T4, T5, T6, T7, T8 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, T3],
+	f3 func(T3) gp.Parser[In, T4],
+	f4 func(T4) gp.Parser[In, T5],
+	f5 func(T5) gp.Parser[In, T6],
+	f6 func(T6) gp.Parser[In, T7],
+	f7 func(T7) gp.Parser[In, T8],
+	f8 func(T8) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(p, f), f2), f3), f4), f5), f6), f7), f8)
+}
+func Bind9[In, Out, T, T2, T3, T4, T5, T6, T7, T8, T9 any](
+	p gp.Parser[In, T],
+	f func(T) gp.Parser[In, T2],
+	f2 func(T2) gp.Parser[In, T3],
+	f3 func(T3) gp.Parser[In, T4],
+	f4 func(T4) gp.Parser[In, T5],
+	f5 func(T5) gp.Parser[In, T6],
+	f6 func(T6) gp.Parser[In, T7],
+	f7 func(T7) gp.Parser[In, T8],
+	f8 func(T8) gp.Parser[In, T9],
+	f9 func(T9) gp.Parser[In, Out],
+) gp.Parser[In, Out] {
+	return gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(gp.Bind(p, f), f2), f3), f4), f5), f6), f7), f8), f9)
+}
+
+func Seq[In, Out, T, T2 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	f func(T, T2) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Return[In](f(x, x2))
+		})
+	})
+}
+func Seq3[In, Out, T, T2, T3 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	p3 gp.Parser[In, T3],
+	f func(T, T2, T3) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Bind(p3, func(x3 T3) gp.Parser[In, Out] {
+				return gp.Return[In](f(x, x2, x3))
+			})
+		})
+	})
+}
+func Seq4[In, Out, T, T2, T3, T4 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	p3 gp.Parser[In, T3],
+	p4 gp.Parser[In, T4],
+	f func(T, T2, T3, T4) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Bind(p3, func(x3 T3) gp.Parser[In, Out] {
+				return gp.Bind(p4, func(x4 T4) gp.Parser[In, Out] {
+					return gp.Return[In](f(x, x2, x3, x4))
+				})
+			})
+		})
+	})
+}
+func Seq5[In, Out, T, T2, T3, T4, T5 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	p3 gp.Parser[In, T3],
+	p4 gp.Parser[In, T4],
+	p5 gp.Parser[In, T5],
+	f func(T, T2, T3, T4, T5) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Bind(p3, func(x3 T3) gp.Parser[In, Out] {
+				return gp.Bind(p4, func(x4 T4) gp.Parser[In, Out] {
+					return gp.Bind(p5, func(x5 T5) gp.Parser[In, Out] {
+						return gp.Return[In](f(x, x2, x3, x4, x5))
+					})
+				})
+			})
+		})
+	})
+}
+func Seq6[In, Out, T, T2, T3, T4, T5, T6 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	p3 gp.Parser[In, T3],
+	p4 gp.Parser[In, T4],
+	p5 gp.Parser[In, T5],
+	p6 gp.Parser[In, T6],
+	f func(T, T2, T3, T4, T5, T6) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Bind(p3, func(x3 T3) gp.Parser[In, Out] {
+				return gp.Bind(p4, func(x4 T4) gp.Parser[In, Out] {
+					return gp.Bind(p5, func(x5 T5) gp.Parser[In, Out] {
+						return gp.Bind(p6, func(x6 T6) gp.Parser[In, Out] {
+							return gp.Return[In](f(x, x2, x3, x4, x5, x6))
+						})
+					})
+				})
+			})
+		})
+	})
+}
+func Seq7[In, Out, T, T2, T3, T4, T5, T6, T7 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	p3 gp.Parser[In, T3],
+	p4 gp.Parser[In, T4],
+	p5 gp.Parser[In, T5],
+	p6 gp.Parser[In, T6],
+	p7 gp.Parser[In, T7],
+	f func(T, T2, T3, T4, T5, T6, T7) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Bind(p3, func(x3 T3) gp.Parser[In, Out] {
+				return gp.Bind(p4, func(x4 T4) gp.Parser[In, Out] {
+					return gp.Bind(p5, func(x5 T5) gp.Parser[In, Out] {
+						return gp.Bind(p6, func(x6 T6) gp.Parser[In, Out] {
+							return gp.Bind(p7, func(x7 T7) gp.Parser[In, Out] {
+								return gp.Return[In](f(x, x2, x3, x4, x5, x6, x7))
+							})
+						})
+					})
+				})
+			})
+		})
+	})
+}
+func Seq8[In, Out, T, T2, T3, T4, T5, T6, T7, T8 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	p3 gp.Parser[In, T3],
+	p4 gp.Parser[In, T4],
+	p5 gp.Parser[In, T5],
+	p6 gp.Parser[In, T6],
+	p7 gp.Parser[In, T7],
+	p8 gp.Parser[In, T8],
+	f func(T, T2, T3, T4, T5, T6, T7, T8) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Bind(p3, func(x3 T3) gp.Parser[In, Out] {
+				return gp.Bind(p4, func(x4 T4) gp.Parser[In, Out] {
+					return gp.Bind(p5, func(x5 T5) gp.Parser[In, Out] {
+						return gp.Bind(p6, func(x6 T6) gp.Parser[In, Out] {
+							return gp.Bind(p7, func(x7 T7) gp.Parser[In, Out] {
+								return gp.Bind(p8, func(x8 T8) gp.Parser[In, Out] {
+									return gp.Return[In](f(x, x2, x3, x4, x5, x6, x7, x8))
+								})
+							})
+						})
+					})
+				})
+			})
+		})
+	})
+}
+func Seq9[In, Out, T, T2, T3, T4, T5, T6, T7, T8, T9 any](
+	p gp.Parser[In, T],
+	p2 gp.Parser[In, T2],
+	p3 gp.Parser[In, T3],
+	p4 gp.Parser[In, T4],
+	p5 gp.Parser[In, T5],
+	p6 gp.Parser[In, T6],
+	p7 gp.Parser[In, T7],
+	p8 gp.Parser[In, T8],
+	p9 gp.Parser[In, T9],
+	f func(T, T2, T3, T4, T5, T6, T7, T8, T9) Out,
+) gp.Parser[In, Out] {
+	return gp.Bind(p, func(x T) gp.Parser[In, Out] {
+		return gp.Bind(p2, func(x2 T2) gp.Parser[In, Out] {
+			return gp.Bind(p3, func(x3 T3) gp.Parser[In, Out] {
+				return gp.Bind(p4, func(x4 T4) gp.Parser[In, Out] {
+					return gp.Bind(p5, func(x5 T5) gp.Parser[In, Out] {
+						return gp.Bind(p6, func(x6 T6) gp.Parser[In, Out] {
+							return gp.Bind(p7, func(x7 T7) gp.Parser[In, Out] {
+								return gp.Bind(p8, func(x8 T8) gp.Parser[In, Out] {
+									return gp.Bind(p9, func(x9 T9) gp.Parser[In, Out] {
+										return gp.Return[In](f(x, x2, x3, x4, x5, x6, x7, x8, x9))
+									})
+								})
+							})
+						})
+					})
+				})
+			})
+		})
+	})
+}

naive/naive_test.go

@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: Unlicense
+
+package naive_test
+
+import (
+	"testing"
+
+	"git.codemonkeysoftware.net/b/gigaparsec"
+	"git.codemonkeysoftware.net/b/gigaparsec/naive"
+)
+
+func BenchmarkBind5(b *testing.B) {
+	type Bind5T = func(p gigaparsec.Parser[byte, byte], f func(byte) gigaparsec.Parser[byte, byte], f2 func(byte) gigaparsec.Parser[byte, byte], f3 func(byte) gigaparsec.Parser[byte, byte], f4 func(byte) gigaparsec.Parser[byte, byte], f5 func(byte) gigaparsec.Parser[byte, byte]) gigaparsec.Parser[byte, byte]
+
+	f := func(b byte) gigaparsec.Parser[byte, byte] {
+		return gigaparsec.Return[byte](b + 1)
+	}
+	p := func(bind5 Bind5T) gigaparsec.Parser[byte, byte] {
+		// gigaparsec.Bind5()
+		return bind5(gigaparsec.Match(byte(0)), f, f, f, f, f)
+	}
+	input := gigaparsec.SliceReaderAt[byte]{0}
+	b.Run("gigaparsec.Bind5", func(b *testing.B) {
+		for range b.N {
+			p(gigaparsec.Bind5).Run(input)
+		}
+
+	})
+	b.Run("naïve.Bind5", func(b *testing.B) {
+		for range b.N {
+			p(naive.Bind5).Run(input)
+		}
+	})
+}
+
+func BenchmarkBind9(b *testing.B) {
+	type Bind9T = func(p gigaparsec.Parser[byte, byte], f func(byte) gigaparsec.Parser[byte, byte], f2 func(byte) gigaparsec.Parser[byte, byte], f3 func(byte) gigaparsec.Parser[byte, byte], f4 func(byte) gigaparsec.Parser[byte, byte], f5 func(byte) gigaparsec.Parser[byte, byte], f6 func(byte) gigaparsec.Parser[byte, byte], f7 func(byte) gigaparsec.Parser[byte, byte], f8 func(byte) gigaparsec.Parser[byte, byte], f9 func(byte) gigaparsec.Parser[byte, byte]) gigaparsec.Parser[byte, byte]
+
+	f := func(b byte) gigaparsec.Parser[byte, byte] {
+		return gigaparsec.Return[byte](b + 1)
+	}
+	p := func(bind5 Bind9T) gigaparsec.Parser[byte, byte] {
+		// gigaparsec.Bind5()
+		return bind5(gigaparsec.Match(byte(0)), f, f, f, f, f, f, f, f, f)
+	}
+	input := gigaparsec.SliceReaderAt[byte]{0}
+	b.Run("gigaparsec.Bind9", func(b *testing.B) {
+		for range b.N {
+			p(gigaparsec.Bind9).Run(input)
+		}
+
+	})
+	b.Run("naive.Bind9", func(b *testing.B) {
+		for range b.N {
+			p(naive.Bind9).Run(input)
+		}
+	})
+}
+
+func BenchmarkSeq5(b *testing.B) {
+	type P = gigaparsec.Parser[byte, byte]
+	type Seq5T = func(P, P, P, P, P, func(byte, byte, byte, byte, byte) byte) P
+
+	zero := gigaparsec.Return[byte, byte](0)
+
+	f := func(a, b, c, d, e byte) byte {
+		return a + b + c + d + e
+	}
+	p := func(seq5 Seq5T) P {
+		return seq5(zero, zero, zero, zero, zero, f)
+	}
+	input := gigaparsec.SliceReaderAt[byte]{0}
+	b.Run("gigaparsec.Seq5", func(b *testing.B) {
+		for range b.N {
+			p(gigaparsec.Seq5).Run(input)
+		}
+	})
+	b.Run("naive.Seq5", func(b *testing.B) {
+		for range b.N {
+			p(naive.Seq5).Run(input)
+		}
+	})
+}
+
+func BenchmarkSeq9(b *testing.B) {
+	type P = gigaparsec.Parser[byte, byte]
+	type Seq9T = func(P, P, P, P, P, P, P, P, P, func(byte, byte, byte, byte, byte, byte, byte, byte, byte) byte) P
+
+	zero := gigaparsec.Return[byte, byte](0)
+
+	f := func(a, b, c, d, e, f, g, h, i byte) byte {
+		return a + b + c + d + e + f + g + h + i
+	}
+	p := func(seq9 Seq9T) P {
+		return seq9(zero, zero, zero, zero, zero, zero, zero, zero, zero, f)
+	}
+	input := gigaparsec.SliceReaderAt[byte]{0}
+	b.Run("gigaparsec.Seq9", func(b *testing.B) {
+		for range b.N {
+			p(gigaparsec.Seq9).Run(input)
+		}
+	})
+	b.Run("naive.Seq9", func(b *testing.B) {
+		for range b.N {
+			p(naive.Seq9).Run(input)
+		}
+	})
+}

parser_test.go

@@ -4,6 +4,8 @@ package gigaparsec_test
 
 import (
 	"bytes"
+	"errors"
+	"fmt"
 	"testing"
 
 	"git.codemonkeysoftware.net/b/gigaparsec"
@@ -14,7 +16,7 @@ import (
 	"pgregory.net/rapid"
 )
 
-func Todo(t *testing.T) {
+func Todo[T interface{ Errorf(string, ...any) }](t T) {
 	t.Errorf("TODO")
 }
 
@@ -29,8 +31,7 @@ func hasPrefix(prefix []byte) func([]byte) bool {
 func TestSlice(t *testing.T) {
 	assertParseFails := func(t rapid.TB, input []byte, p gigaparsec.Parser[byte, []byte]) {
 		t.Helper()
-		start := gigaparsec.MakeState(bytes.NewReader(input))
-		result, err := p(start)
+		result, err := p.RunToResult(bytes.NewReader(input))
 		must.NoError(t, err)
 		success, _, _ := result.Status()
 		test.False(t, success)
@@ -56,7 +57,7 @@ func TestSlice(t *testing.T) {
 		expectedErr := generator.Error().Draw(t, "expectedErr")
 		r := ptest.ErrReaderAt(expectedErr)
 		s := rapid.SliceOfN(rapid.Byte(), 0, 100).Draw(t, "s")
-		result, err := gigaparsec.MatchSlice(s)(gigaparsec.MakeState(r))
+		result, err := gigaparsec.MatchSlice(s).RunToResult(r)
 		test.ErrorIs(t, err, expectedErr)
 		success, _, _ := result.Status()
 		test.False(t, success)
@@ -65,9 +66,8 @@ func TestSlice(t *testing.T) {
 		input := rapid.SliceOfN(rapid.Byte(), 1, -1).Draw(t, "input")
 		s := rapid.Map(rapid.IntRange(0, len(input)),
 			func(n int) []byte { return input[:n] }).Draw(t, "s")
-		start := gigaparsec.MakeState(bytes.NewReader(input))
 
-		result, err := gigaparsec.MatchSlice(s)(start)
+		result, err := gigaparsec.MatchSlice(s).RunToResult(bytes.NewReader(input))
 		must.NoError(t, err)
 		success, value, next := result.Status()
 		test.True(t, success)
@@ -88,7 +88,7 @@ func TestBind(t *testing.T) {
 	t.Run("returns an error if the second parser returns an error", Todo)
 	t.Run("succeeds if both parsers succeed", rapid.MakeCheck(func(t *rapid.T) {
 		// s := rapid.SliceOfN(rapid.Byte(), 0, 100)
-		t.Errorf("TODO")
+		Todo(t)
 	}))
 	/*
 		If the first parser fails, then consumption depends on the first parser.
@@ -107,7 +107,7 @@ func TestBind(t *testing.T) {
 		p := makeParser(pConsume)
 		q := func(struct{}) gigaparsec.Parser[byte, struct{}] { return makeParser(qConsume) }
 
-		result, err := gigaparsec.Bind(p, q)(gigaparsec.MakeState(bytes.NewReader(nil)))
+		result, err := gigaparsec.Bind(p, q).RunToResult(bytes.NewReader(nil))
 		must.NoError(t, err)
 		must.EqOp(t, pConsume || qConsume, result.Consumed())
 	}))
@@ -125,8 +125,31 @@ func TestSatisfy(t *testing.T) {
 	Todo(t)
 }
 
-func Try(t *testing.T) {
-	Todo(t)
+func TestTry(t *testing.T) {
+	type R = ptest.ForcedResult
+	var cases = []struct{ P, TryP R }{
+		{P: R{Succeed: false, Consume: false}, TryP: R{Succeed: false, Consume: false}},
+		{P: R{Succeed: false, Consume: true}, TryP: R{Succeed: false, Consume: false}},
+		{P: R{Succeed: true, Consume: false}, TryP: R{Succeed: true, Consume: false}},
+		{P: R{Succeed: true, Consume: true}, TryP: R{Succeed: true, Consume: true}},
+	}
+	for _, c := range cases {
+		t.Run(fmt.Sprintf("%+v", c.P), func(t *testing.T) {
+			result, err := gigaparsec.Try(ptest.ForceResult).RunToResult(gigaparsec.SliceReaderAt[R]{c.P})
+			succeeded, _, _ := result.Status()
+			must.NoError(t, err)
+			test.EqOp(t, c.TryP.Succeed, succeeded)
+			test.EqOp(t, c.TryP.Consume, result.Consumed())
+		})
+	}
+	t.Run("fails on error", func(t *testing.T) {
+		expectedErr := errors.New("it broke")
+		p := gigaparsec.Try(gigaparsec.Match(byte(0)))
+		result, err := p.RunToResult(ptest.ErrReaderAt(expectedErr))
+		succeeded, _, _ := result.Status()
+		test.ErrorIs(t, err, expectedErr)
+		test.False(t, succeeded)
+	})
 }
 
 func TestLabel(t *testing.T) {
@@ -138,24 +161,57 @@ func TestEnd(t *testing.T) {
 }
 
 func TestRepeat(t *testing.T) {
-	t.Run("succeeds iff number of successes ≥ minCount", rapid.MakeCheck(func(t *rapid.T) {
-		const good byte = 'o'
-		const bad byte = 'x'
 	const maxParses = 100
-
+	t.Run("succeeds iff number of successes ≥ minCount", rapid.MakeCheck(func(t *rapid.T) {
 		minCount := rapid.IntRange(0, maxParses).Draw(t, "minCount")
 		successes := rapid.IntRange(0, maxParses).Draw(t, "successes")
+		shouldSucceed := successes >= minCount
 
-		input := append(ptest.SliceOfN(good, successes), bad)
-		p := gigaparsec.Repeat(minCount, gigaparsec.Match(good))
-		result, err := p(gigaparsec.MakeState(bytes.NewReader(input)))
+		input := append(ptest.SliceOfN(true, successes), false)
+		p := gigaparsec.Repeat(minCount, gigaparsec.Match(true))
+		result, err := p.RunToResult(gigaparsec.SliceReaderAt[bool](input))
 
 		must.NoError(t, err)
-		success, _, _ := result.Status()
-		test.EqOp(t, successes >= minCount, success, test.Sprint("expected successes ≥ minCount"))
+		success, _, next := result.Status()
+		test.EqOp(t, shouldSucceed, success)
+		if success {
+			test.EqOp(t, uint64(successes), next.Pos())
+		}
 	}))
-	t.Run("consumes iff at least one application consumes", Todo)
-	t.Run("fails on error", Todo)
-	t.Run("position is unchanged on failure", Todo)
-	t.Run("position follows last success on overall success", Todo)
+	t.Run("consumes iff at least one application consumes", rapid.MakeCheck(func(t *rapid.T) {
+		input := rapid.Map(rapid.SliceOfN(rapid.Just(ptest.ForcedResult{Succeed: true}), 0, 100),
+			func(ts []ptest.ForcedResult) []ptest.ForcedResult { return append(ts, ptest.ForcedResult{}) }).Draw(t, "input")
+		consumeAt := rapid.Ptr(rapid.IntRange(0, len(input)-1), true).Draw(t, "consumeAt")
+		if consumeAt != nil {
+			input[*consumeAt].Consume = true
+		}
+		shouldConsume := consumeAt != nil
+
+		result, err := gigaparsec.Repeat(0, ptest.ForceResult).RunToResult(gigaparsec.SliceReaderAt[ptest.ForcedResult](input))
+		must.NoError(t, err)
+		test.EqOp(t, shouldConsume, result.Consumed())
+	}))
+
+	t.Run("does not consume on empty input", func(t *testing.T) {
+		p := gigaparsec.Repeat(0, gigaparsec.Match(0))
+		result, err := p.RunToResult(gigaparsec.SliceReaderAt[int](nil))
+		must.NoError(t, err)
+		must.False(t, result.Consumed())
+	})
+	t.Run("fails on error", func(t *testing.T) {
+		expectedErr := errors.New("it broke")
+		p := gigaparsec.Repeat(0, gigaparsec.Match(byte(0)))
+		result, err := p.RunToResult(ptest.ErrReaderAt(expectedErr))
+		succeeded, _, _ := result.Status()
+		test.ErrorIs(t, err, expectedErr)
+		test.False(t, succeeded)
+	})
+}
+
+func TestBracket(t *testing.T) {
+	Todo(t)
+}
+
+func TestWhere(t *testing.T) {
+	Todo(t)
 }

seq.go

@@ -4,7 +4,8 @@
 
 package gigaparsec
 
-func Seq2[In, Out, T, T2 any](
+// Seq runs 2 parsers in sequence and maps their collected results with f.
+func Seq[In, Out, T, T2 any](
 	p Parser[In, T],
 	p2 Parser[In, T2],
 	f func(T, T2) Out,
@@ -34,10 +35,11 @@ func Seq2[In, Out, T, T2 any](
 		}
 
 		final := f(val, val2)
-		return Succeed(anyConsumed, final, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
 	}
 }
 
+// Seq3 runs 3 parsers in sequence and maps their collected results with f.
 func Seq3[In, Out, T, T2, T3 any](
 	p Parser[In, T],
 	p2 Parser[In, T2],
@@ -79,10 +81,11 @@ func Seq3[In, Out, T, T2, T3 any](
 		}
 
 		final := f(val, val2, val3)
-		return Succeed(anyConsumed, final, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
 	}
 }
 
+// Seq4 runs 4 parsers in sequence and maps their collected results with f.
 func Seq4[In, Out, T, T2, T3, T4 any](
 	p Parser[In, T],
 	p2 Parser[In, T2],
@@ -135,10 +138,11 @@ func Seq4[In, Out, T, T2, T3, T4 any](
 		}
 
 		final := f(val, val2, val3, val4)
-		return Succeed(anyConsumed, final, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
 	}
 }
 
+// Seq5 runs 5 parsers in sequence and maps their collected results with f.
 func Seq5[In, Out, T, T2, T3, T4, T5 any](
 	p Parser[In, T],
 	p2 Parser[In, T2],
@@ -202,6 +206,388 @@ func Seq5[In, Out, T, T2, T3, T4, T5 any](
 		}
 
 		final := f(val, val2, val3, val4, val5)
-		return Succeed(anyConsumed, final, next, MessageOK(s.Pos())), nil
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
+	}
+}
+
+// Seq6 runs 6 parsers in sequence and maps their collected results with f.
+func Seq6[In, Out, T, T2, T3, T4, T5, T6 any](
+	p Parser[In, T],
+	p2 Parser[In, T2],
+	p3 Parser[In, T3],
+	p4 Parser[In, T4],
+	p5 Parser[In, T5],
+	p6 Parser[In, T6],
+	f func(T, T2, T3, T4, T5, T6) Out,
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := p2(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := p3(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := p4(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := p5(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := p6(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		final := f(val, val2, val3, val4, val5, val6)
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
+	}
+}
+
+// Seq7 runs 7 parsers in sequence and maps their collected results with f.
+func Seq7[In, Out, T, T2, T3, T4, T5, T6, T7 any](
+	p Parser[In, T],
+	p2 Parser[In, T2],
+	p3 Parser[In, T3],
+	p4 Parser[In, T4],
+	p5 Parser[In, T5],
+	p6 Parser[In, T6],
+	p7 Parser[In, T7],
+	f func(T, T2, T3, T4, T5, T6, T7) Out,
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := p2(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := p3(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := p4(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := p5(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := p6(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		r7, err := p7(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r7.Consumed()
+		success, val7, next := r7.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r7.Message()), nil
+		}
+
+		final := f(val, val2, val3, val4, val5, val6, val7)
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
+	}
+}
+
+// Seq8 runs 8 parsers in sequence and maps their collected results with f.
+func Seq8[In, Out, T, T2, T3, T4, T5, T6, T7, T8 any](
+	p Parser[In, T],
+	p2 Parser[In, T2],
+	p3 Parser[In, T3],
+	p4 Parser[In, T4],
+	p5 Parser[In, T5],
+	p6 Parser[In, T6],
+	p7 Parser[In, T7],
+	p8 Parser[In, T8],
+	f func(T, T2, T3, T4, T5, T6, T7, T8) Out,
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := p2(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := p3(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := p4(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := p5(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := p6(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		r7, err := p7(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r7.Consumed()
+		success, val7, next := r7.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r7.Message()), nil
+		}
+
+		r8, err := p8(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r8.Consumed()
+		success, val8, next := r8.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r8.Message()), nil
+		}
+
+		final := f(val, val2, val3, val4, val5, val6, val7, val8)
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
+	}
+}
+
+// Seq9 runs 9 parsers in sequence and maps their collected results with f.
+func Seq9[In, Out, T, T2, T3, T4, T5, T6, T7, T8, T9 any](
+	p Parser[In, T],
+	p2 Parser[In, T2],
+	p3 Parser[In, T3],
+	p4 Parser[In, T4],
+	p5 Parser[In, T5],
+	p6 Parser[In, T6],
+	p7 Parser[In, T7],
+	p8 Parser[In, T8],
+	p9 Parser[In, T9],
+	f func(T, T2, T3, T4, T5, T6, T7, T8, T9) Out,
+) Parser[In, Out] {
+	return func(s State[In]) (Result[In, Out], error) {
+		var anyConsumed bool
+		var next = s
+
+		r, err := p(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r.Consumed()
+		success, val, next := r.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r.Message()), nil
+		}
+
+		r2, err := p2(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r2.Consumed()
+		success, val2, next := r2.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r2.Message()), nil
+		}
+
+		r3, err := p3(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r3.Consumed()
+		success, val3, next := r3.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r3.Message()), nil
+		}
+
+		r4, err := p4(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r4.Consumed()
+		success, val4, next := r4.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r4.Message()), nil
+		}
+
+		r5, err := p5(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r5.Consumed()
+		success, val5, next := r5.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r5.Message()), nil
+		}
+
+		r6, err := p6(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r6.Consumed()
+		success, val6, next := r6.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r6.Message()), nil
+		}
+
+		r7, err := p7(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r7.Consumed()
+		success, val7, next := r7.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r7.Message()), nil
+		}
+
+		r8, err := p8(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r8.Consumed()
+		success, val8, next := r8.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r8.Message()), nil
+		}
+
+		r9, err := p9(next)
+		if err != nil {
+			return Result[In, Out]{}, err
+		}
+		anyConsumed = anyConsumed || r9.Consumed()
+		success, val9, next := r9.Status()
+		if !success {
+			return Fail[In, Out](anyConsumed, r9.Message()), nil
+		}
+
+		final := f(val, val2, val3, val4, val5, val6, val7, val8, val9)
+		return Succeed(anyConsumed, final, next, s.MessageOK()), nil
 	}
 }

test/helpers.go

@@ -4,6 +4,7 @@
 package test
 
 import (
+	"errors"
 	"io"
 
 	"git.codemonkeysoftware.net/b/gigaparsec"
@@ -34,3 +35,22 @@ func SliceOfN[T any](value T, n int) []T {
 	}
 	return s
 }
+
+type ForcedResult struct{ Succeed, Consume bool }
+
+func ForceResult(state gigaparsec.State[ForcedResult]) (gigaparsec.Result[ForcedResult, struct{}], error) {
+	buf := make([]ForcedResult, 1)
+	_, next, err := state.Read(buf)
+	if errors.Is(err, io.EOF) {
+		return gigaparsec.Fail[ForcedResult, struct{}](false, state.MessageEnd()), nil
+	}
+	if err != nil {
+		return gigaparsec.Result[ForcedResult, struct{}]{}, err
+	}
+	tok := buf[0]
+	if tok.Succeed {
+		return gigaparsec.Succeed(tok.Consume, struct{}{}, next, state.MessageOK()), nil
+	} else {
+		return gigaparsec.Fail[ForcedResult, struct{}](tok.Consume, state.Message("Succeed=false", "Succeed=true")), nil
+	}
+}