85 lines
2.3 KiB
Go
85 lines
2.3 KiB
Go
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package main
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// Helper functions to convert infix notation to RPN and calculates expression result.
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import (
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"fmt"
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"log"
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"strconv"
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"github.com/neonxp/unilex"
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)
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func infixToRPNotation(l *unilex.Lexer) []unilex.Lexem {
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output := []unilex.Lexem{}
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stack := lexemStack{}
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parseLoop:
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for ll := range l.Output { // Read lexems from Lexer output channel, convert starts as soon as first lexems scanned!
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fmt.Printf("Lexem: %+v\n", ll)
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switch {
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case ll.Type == "NUMBER", ll.Type == "OPERATOR" && ll.Value == "!":
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output = append(output, ll)
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case ll.Type == "LP":
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stack.Push(ll)
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case ll.Type == "RP":
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for {
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cl := stack.Pop()
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if cl.Type == "LP" {
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break
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}
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if cl.Type == unilex.LEOF {
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log.Fatalf("No pair for parenthesis at %d", ll.Start)
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}
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output = append(output, cl)
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}
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case ll.Type == "OPERATOR":
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for {
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if stack.Head().Type == "OPERATOR" && (opPriority[stack.Head().Value] > opPriority[ll.Value]) {
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output = append(output, stack.Pop())
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continue
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}
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break
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}
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stack.Push(ll)
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case ll.Type == unilex.LEOF:
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break parseLoop
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}
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}
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for stack.Head().Type != unilex.LEOF {
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output = append(output, stack.Pop())
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}
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return output
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}
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func calculateRPN(rpnLexems []unilex.Lexem) string {
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stack := lexemStack{}
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for _, op := range rpnLexems {
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if op.Type == "NUMBER" {
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stack.Push(op)
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} else {
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switch op.Value {
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case "+":
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a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2+a1, 'f', -1, 64)})
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case "-":
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a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2-a1, 'f', -1, 64)})
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case "*":
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a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2*a1, 'f', -1, 64)})
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case "/":
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a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
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stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2/a1, 'f', -1, 64)})
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}
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}
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}
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return stack.Head().Value
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}
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