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