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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
}
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