fixed IsWhitespace function consideres tabs as whitespace

position.go

@@ -10,7 +10,7 @@ func (p *Position) Advance(rn rune) {
 	p.Index++
 	if rn == '\n' {
 		p.Line++
-		p.Column = 0
+		p.Column = 1
 	} else {
 		p.Column++
 	}

reader.go

@@ -18,7 +18,7 @@ func New(r io.Reader) *Reader {
 	return &Reader{
 		buf: ds.NewArrayStack[posRune](),
 		src: bufio.NewReader(r),
-		pos: &Position{},
+		pos: &Position{Index: 0, Line: 1, Column: 1},
 	}
 }
 
@@ -33,8 +33,8 @@ func (r *Reader) psrn(rn rune) posRune {
 	}
 }
 
-func (r *Reader) Pos() (index, line, column int) {
-	return r.pos.Index, r.pos.Line, r.pos.Column
+func (r *Reader) Pos() Position {
+	return *r.pos
 }
 
 // Rune returns the next rune in r
@@ -176,16 +176,24 @@ func (r *Reader) PeekStringUntil(f ...RuneFunc) (string, error) {
 }
 
 // SkipUntil acts as StringUntil but discards the string
+// The rune for which that function returned false will be unread.
 func (r *Reader) SkipUntil(f ...RuneFunc) error {
 	_, err := r.StringUntil(f...)
+	if err != nil {
 		return err
 	}
+	return r.UnreadRune()
+}
 
-// SkipWhile acts as StringWhile but discards the string
+// SkipWhile acts as StringWhile but discards the string.
+// The rune for which that function returned false will be unread.
 func (r *Reader) SkipWhile(f ...RuneFunc) error {
 	_, err := r.StringWhile(f...)
+	if err != nil {
 		return err
 	}
+	return r.UnreadRune()
+}
 
 // ExpectRune returns true if any function returns true for the next rune read from r
 func (r *Reader) ExpectRune(f ...RuneFunc) (bool, error) {

reader_test.go

@@ -11,8 +11,8 @@ func TestPos(t *testing.T) {
 
 	unread := false
 	for rn, err := r.Rune(); err == nil; rn, err = r.Rune() {
-		index, line, col := r.Pos()
-		fmt.Println(string(rn), index, line, col)
+		pos := r.Pos()
+		fmt.Println(string(rn), pos.Index, pos.Line, pos.Column)
 
 		if !unread && rn == '\n' {
 			for i := 0; i < 5; i++ {

runefunc.go

@@ -12,8 +12,12 @@ func IsSpace(rn rune) bool {
 	return rn == ' '
 }
 
+func IsTab(rn rune) bool {
+	return rn == '\t'
+}
+
 func IsWhitespace(rn rune) bool {
-	return IsSpace(rn) || IsNewLine(rn)
+	return IsSpace(rn) || IsTab(rn) || IsNewLine(rn)
 }
 
 func And(f ...RuneFunc) RuneFunc {