package main import ( "fmt" "github.com/neonxp/unilex" ) const ( LP unilex.LexType = iota RP NUMBER OPERATOR ) func main() { l := unilex.New("10 * (20.0 + 30.0)") go l.Run(lexExpression) // Start lexer // Read infix expression lexems from lexer and convert them to RPN (reverse polish notation) rpn := infixToRPNotation(l) fmt.Println("RPN:", rpn) // Calculate RPN result := calculateRPN(rpn) fmt.Println("Result:", result) } func lexExpression(l *unilex.Lexer) unilex.StateFunc { l.AcceptWhile(" \t") l.Ignore() // Ignore whitespaces switch { case l.Accept("("): l.Emit(LP) case l.Accept(")"): l.Emit(RP) case unilex.ScanNumber(l): l.Emit(NUMBER) case l.Accept("+-*/^!"): l.Emit(OPERATOR) case l.Peek() == unilex.EOF: return nil default: return l.Errorf("Unexpected symbol") } return lexExpression }