81 lines
1.2 KiB
Go
81 lines
1.2 KiB
Go
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package runner
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type Scanner struct {
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source string
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// State.
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tokens []Token
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start int
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current int
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line int
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}
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func NewScanner(source string) *Scanner {
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return &Scanner{
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source: source,
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tokens: []Token{},
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start: 0,
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current: 0,
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line: 1,
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}
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}
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func (s *Scanner) ScanTokens() []Token {
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for !s.isAtEnd() {
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s.start = s.current
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s.scanToken()
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}
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s.tokens = append(s.tokens, NewToken(EOF, "", nil, s.line))
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return s.tokens
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}
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func (s *Scanner) scanToken() {
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c := s.advance()
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switch c {
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case '(':
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s.addToken(LPAREN)
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case ')':
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s.addToken(RPAREN)
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case '{':
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s.addToken(LBRACE)
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case '}':
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s.addToken(RBRACE)
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case ',':
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s.addToken(COMMA)
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case '.':
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s.addToken(DOT)
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case '-':
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s.addToken(MINUS)
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case '+':
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s.addToken(PLUS)
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case ';':
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s.addToken(SEMI)
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case '*':
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s.addToken(STAR)
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}
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}
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func (s *Scanner) advance() byte {
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idx := s.current
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s.current += 1
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return s.source[idx]
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}
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func (s *Scanner) addToken(typ TokenType) {
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s.addTokenWithLiteral(typ, nil)
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}
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func (s *Scanner) addTokenWithLiteral(typ TokenType, literal interface{}) {
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lexme := s.source[s.start:s.current]
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s.tokens = append(
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s.tokens,
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NewToken(typ, lexme, literal, s.line),
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)
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}
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func (s *Scanner) isAtEnd() bool {
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return s.current >= len(s.source)
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}
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