lexer: introduce Error{}

Signed-off-by: Alejandro Mery <amery@jpi.io>

lexer/error.go

@@ -1,7 +1,6 @@
 package lexer
 
 import (
-	"errors"
 	"fmt"
 	"strings"
 )
@@ -10,14 +9,6 @@ var (
 	_ error = (*Error)(nil)
 )
 
-var (
-	// ErrUnacceptableRune indicates the read rune isn't acceptable in the context
-	ErrUnacceptableRune = errors.New("rune not acceptable in context")
-
-	// ErrNotImplemented indicates something hasn't been implemented yet
-	ErrNotImplemented = errors.New("not implemented")
-)
-
 // Error represents a generic parsing error
 type Error struct {
 	Filename string

lexer/lexer.go

@@ -1,31 +1,17 @@
 // Package lexer provides basic helpers to implement parsers
 package lexer
 
-import (
-	"errors"
-	"io"
-)
-
 // StateFn is a State Function of the parser
 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 {
-	for fn != nil {
-		var err error
+	var err error
 
+	for fn != nil && err == nil {
 		fn, err = fn()
-		switch {
-		case errors.Is(err, io.EOF):
-			// EOF
-			return nil
-		case err != nil:
-			// failed
-			return err
-		}
 	}
 
-	// ended
-	return nil
+	return err
 }

lexer/position.go

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

lexer/runes.go

@@ -1,41 +0,0 @@
-package lexer
-
-import (
-	"strings"
-	"unicode"
-)
-
-// NewIsNot generates a rune condition checker that reverses the
-// decision of the given checker.
-func NewIsNot(cond func(rune) bool) func(rune) bool {
-	return func(r rune) bool {
-		return !cond(r)
-	}
-}
-
-// NewIsIn generates a rune condition checker that accepts runes
-// contained on the provided string
-func NewIsIn(s string) func(rune) bool {
-	return func(r rune) bool {
-		return strings.ContainsRune(s, r)
-	}
-}
-
-// NewIsOneOf generates a run condition checker that accepts runes
-// accepted by any of the given checkers
-func NewIsOneOf(s ...func(rune) bool) func(rune) bool {
-	return func(r rune) bool {
-		for _, cond := range s {
-			if cond(r) {
-				return true
-			}
-		}
-		return false
-	}
-}
-
-// IsSpace reports whether the rune is a space character as
-// defined by Unicode's White Space property
-func IsSpace(r rune) bool {
-	return unicode.IsSpace(r)
-}