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223 lines
4.8 KiB
223 lines
4.8 KiB
package scanner
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import (
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"bufio"
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"io"
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"github.com/brettlangdon/gython/errorcode"
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"github.com/brettlangdon/gython/token"
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)
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var EOF rune = 0
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var MAXINDENT int = 100
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type Scanner struct {
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state errorcode.ErrorCode
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reader *bufio.Reader
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currentPosition *Position
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positionBuffer []*Position
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currentLine int
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currentColumn int
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}
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func NewScanner(r io.Reader) *Scanner {
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return &Scanner{
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state: errorcode.E_OK,
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reader: bufio.NewReader(r),
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positionBuffer: make([]*Position, 0),
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currentLine: 1,
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currentColumn: 0,
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}
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}
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func (scanner *Scanner) nextPosition() *Position {
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if len(scanner.positionBuffer) > 0 {
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last := len(scanner.positionBuffer) - 1
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scanner.currentPosition = scanner.positionBuffer[last]
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scanner.positionBuffer = scanner.positionBuffer[0:last]
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return scanner.currentPosition
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}
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next, _, err := scanner.reader.ReadRune()
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if err != nil {
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scanner.state = errorcode.E_EOF
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next = EOF
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scanner.currentLine++
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scanner.currentColumn = 0
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}
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pos := &Position{
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Char: next,
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Line: scanner.currentLine,
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Column: scanner.currentColumn,
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}
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scanner.currentColumn++
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if next == '\n' || next == EOF {
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scanner.currentLine++
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scanner.currentColumn = 0
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}
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return pos
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}
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func (scanner *Scanner) unreadPosition(pos *Position) {
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scanner.positionBuffer = append(scanner.positionBuffer, pos)
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}
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func (scanner *Scanner) parseQuoted(positions *Positions, quote rune) *token.Token {
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// Determine quote size, 1 or 3 (e.g. 'string', '''string''')
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quoteSize := 1
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endQuoteSize := 0
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pos := scanner.nextPosition()
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if pos.Char == quote {
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pos2 := scanner.nextPosition()
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if pos2.Char == quote {
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positions.Append(pos)
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positions.Append(pos2)
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quoteSize = 3
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} else {
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scanner.unreadPosition(pos2)
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endQuoteSize = 1
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}
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} else {
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scanner.unreadPosition(pos)
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}
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for {
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if endQuoteSize == quoteSize {
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break
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}
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pos = scanner.nextPosition()
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positions.Append(pos)
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if pos.Char == EOF {
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return positions.AsToken(token.ERRORTOKEN)
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}
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if quoteSize == 1 && pos.Char == '\n' {
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return positions.AsToken(token.ERRORTOKEN)
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}
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if pos.Char == quote {
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endQuoteSize += 1
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} else {
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endQuoteSize = 0
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if pos.Char == '\\' {
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pos = scanner.nextPosition()
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}
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}
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}
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return positions.AsToken(token.STRING)
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}
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func (scanner *Scanner) NextToken() *token.Token {
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positions := NewPositions()
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pos := scanner.nextPosition()
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// skip spaces
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for {
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if pos.Char != ' ' && pos.Char != '\t' {
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break
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}
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pos = scanner.nextPosition()
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}
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// skip comments
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if pos.Char == '#' {
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for {
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pos = scanner.nextPosition()
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if pos.Char == EOF || pos.Char == '\n' {
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break
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}
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}
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}
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positions.Append(pos)
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switch ch := pos.Char; {
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case ch == EOF:
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id := token.ENDMARKER
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if scanner.state != errorcode.E_EOF {
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id = token.ERRORTOKEN
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}
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return positions.AsToken(id)
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case IsIdentifierStart(ch):
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// Parse Identifier
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saw_b, saw_r, saw_u := false, false, false
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for {
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if !(saw_b || saw_u) && (ch == 'b' || ch == 'B') {
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saw_b = true
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} else if !(saw_b || saw_u || saw_r) && (ch == 'u' || ch == 'U') {
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saw_u = true
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} else if !(saw_r || saw_u) && (ch == 'r' || ch == 'R') {
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saw_r = true
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} else {
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break
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}
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pos = scanner.nextPosition()
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if IsQuote(pos.Char) {
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positions.Append(pos)
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return scanner.parseQuoted(positions, pos.Char)
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}
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}
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pos = scanner.nextPosition()
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for IsIdentifierChar(pos.Char) {
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positions.Append(pos)
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pos = scanner.nextPosition()
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}
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scanner.unreadPosition(pos)
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return positions.AsToken(token.NAME)
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case ch == '\n':
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return positions.AsToken(token.NEWLINE)
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case ch == '.':
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pos2 := scanner.nextPosition()
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if IsDigit(pos2.Char) {
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// Parse Number
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} else if pos2.Char == '.' {
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positions.Append(pos2)
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pos3 := scanner.nextPosition()
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if pos3.Char == '.' {
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positions.Append(pos3)
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return positions.AsToken(token.ELLIPSIS)
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}
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scanner.unreadPosition(pos3)
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}
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scanner.unreadPosition(pos2)
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return positions.AsToken(token.DOT)
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case IsDigit(ch):
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// Parse Number
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case IsQuote(ch):
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// Parse String
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return scanner.parseQuoted(positions, ch)
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case ch == '\\':
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// Parse Continuation
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default:
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// Two and Three character operators
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pos2 := scanner.nextPosition()
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op2Id := GetTwoCharTokenID(pos.Char, pos2.Char)
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if op2Id != token.OP {
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positions.Append(pos2)
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pos3 := scanner.nextPosition()
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op3Id := GetThreeCharTokenID(pos.Char, pos2.Char, pos3.Char)
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if op3Id != token.OP {
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positions.Append(pos3)
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return positions.AsToken(op3Id)
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}
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scanner.unreadPosition(pos3)
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return positions.AsToken(op2Id)
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}
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scanner.unreadPosition(pos2)
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}
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switch pos.Char {
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case '(', '[', '{':
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// Increment indentation level
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// scanner.indentationLevel++
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break
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case ')', ']', '}':
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// Decrement indentation level
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// scanner.indentationLevel--
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break
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}
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opId := GetOneCharTokenID(pos.Char)
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return positions.AsToken(opId)
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}
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