Merge pull request 'lexer: Reader.Accept(), AcceptAll(), and StateFn' (#5)

Reviewed-on: #5

lexer/error.go

@@ -0,0 +1,45 @@
+package lexer
+
+import (
+	"fmt"
+	"strings"
+)
+
+var (
+	_ error = (*Error)(nil)
+)
+
+// Error represents a generic parsing error
+type Error struct {
+	Filename string
+	Line     int
+	Column   int
+
+	Content string
+	Err     error
+}
+
+func (err Error) Error() string {
+	var s []string
+
+	switch {
+	case err.Line > 0 || err.Column > 0:
+		s = append(s, fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column))
+	case err.Filename != "":
+		s = append(s, err.Filename)
+	}
+
+	if err.Err != nil {
+		s = append(s, err.Err.Error())
+	}
+
+	if err.Content != "" {
+		s = append(s, fmt.Sprintf("%q", err.Content))
+	}
+
+	return strings.Join(s, ": ")
+}
+
+func (err Error) Unwrap() error {
+	return err.Err
+}

lexer/lexer.go

@@ -1,36 +1,10 @@
 // Package lexer provides basic helpers to implement parsers
 package lexer
 
-import "io"
+import (
-
+	"errors"
-// Lexer adds Accept and AcceptAll support to a
+	"io"
-// [io.RuneScanner]
+)
-type Lexer struct {
-	io.RuneScanner
-}
-
-// Accept consumes a rune from the source if it meets the condition.
-// it returns true if the condition was met and false if it wasn't.
-func (p Lexer) Accept(cond func(rune) bool) bool {
-	return Accept(p, cond)
-}
-
-// AcceptAll consumes runes from the source as long as they meet the
-// condition. it returns true if the condition was met for at least one rune,
-// and false if it wasn't.
-func (p Lexer) AcceptAll(cond func(rune) bool) bool {
-	return AcceptAll(p, cond)
-}
-
-// NewLexer extends a [io.RuneScanner] with Accept()/AcceptAll()
-// functionality
-func NewLexer(src io.RuneScanner) *Lexer {
-	if src == nil {
-		return nil
-	}
-
-	return &Lexer{src}
-}
 
 // StateFn is a State Function of the parser
 type StateFn func() (StateFn, error)
@@ -38,46 +12,20 @@ type StateFn func() (StateFn, error)
 // Run runs a state machine until the state function either
 // returns nil or an error
 func Run(fn StateFn) error {
-	var err error
+	for fn != nil {
+		var err error
 
-	for fn != nil && err == nil {
 		fn, err = fn()
-	}
-
-	return err
-}
-
-// Accept consumes a rune from the source if it meets the condition.
-// it returns true if the condition was met and false if it wasn't.
-func Accept(src io.RuneScanner, cond func(r rune) bool) bool {
-	r, _, err := src.ReadRune()
-	switch {
-	case err != nil:
-		return false
-	case cond(r):
-		return true
-	default:
-		_ = src.UnreadRune()
-		return false
-	}
-}
-
-// AcceptAll consumes runes from the source as long as they meet the
-// condition. it returns true if the condition was met for at least one rune,
-// and false if it wasn't.
-func AcceptAll(src io.RuneScanner, cond func(r rune) bool) bool {
-	var accepted bool
-
-	for {
-		r, _, err := src.ReadRune()
 		switch {
+		case errors.Is(err, io.EOF):
+			// EOF
+			return nil
 		case err != nil:
-			return accepted
+			// failed
-		case cond(r):
+			return err
-			accepted = true
-		default:
-			_ = src.UnreadRune()
-			return accepted
 		}
 	}
+
+	// ended
+	return nil
 }

lexer/position.go

@@ -41,28 +41,26 @@ func (p *Position) Step() {
 	p.Column++
 }
 
-// Next returns a new Position one rune forward
+// StepN moves the column N places forward
-// on the line
+func (p *Position) StepN(n int) {
-func (p Position) Next() Position {
 	if p.Line == 0 {
 		p.Reset()
 	}
 
-	return Position{
+	switch {
-		Line:   p.Line,
+	case n > 0:
-		Column: p.Column + 1,
+		p.Column += n
+	default:
+		panic(fmt.Errorf("invalid %v increment", n))
 	}
 }
 
-// NextLine returns a new Position at the begining of the next
+// StepLine moves position to the start of the next line
-// line.
+func (p *Position) StepLine() {
-func (p Position) NextLine() Position {
 	if p.Line == 0 {
 		p.Reset()
 	}
 
-	return Position{
+	p.Line++
-		Line:   p.Line + 1,
+	p.Column = 1
-		Column: 1,
-	}
 }

lexer/reader.go

@@ -1,4 +1,4 @@
-package runes
+package lexer
 
 import (
 	"bytes"
@@ -168,7 +168,8 @@ func (b *Reader) ReadRune() (rune, int, error) {
 
 	// decode rune
 	r, l := utf8.DecodeRune(b.buf[b.cursor:])
-
+	// step over
+	b.cursor += l
 	// and remember for UnreadRune()
 	b.lastRuneSize = l
 
@@ -197,6 +198,41 @@ func (b *Reader) PeekRune() (rune, int, error) {
 	return r, l, err
 }
 
+// Accept consumes a rune from the source if it meets the condition.
+// it returns true if the condition was met and false if it wasn't.
+func (b *Reader) Accept(cond func(r rune) bool) bool {
+	r, _, err := b.ReadRune()
+	switch {
+	case err != nil:
+		return false
+	case cond(r):
+		return true
+	default:
+		_ = b.UnreadRune()
+		return false
+	}
+}
+
+// AcceptAll consumes runes from the source as long as they meet the
+// condition. it returns true if the condition was met for at least one rune,
+// and false if it wasn't.
+func (b *Reader) AcceptAll(cond func(r rune) bool) bool {
+	var accepted bool
+
+	for {
+		r, _, err := b.ReadRune()
+		switch {
+		case err != nil:
+			return accepted
+		case cond(r):
+			accepted = true
+		default:
+			_ = b.UnreadRune()
+			return accepted
+		}
+	}
+}
+
 // NewReader creates a new runes [Reader] using the given [io.Reader]
 func NewReader(r io.Reader) *Reader {
 	if r == nil {

runes/docs.go

@@ -1,2 +0,0 @@
-// Package runes helps us work with runes
-package runes