57 lines
1,023 B
Go
57 lines
1,023 B
Go
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package main
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import (
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"fmt"
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"strings"
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)
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func print(expr Expr) string {
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switch e := expr.(type) {
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case Binary:
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return parenthesize(e.operator.Lexeme,
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e.left,
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e.right)
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case Grouping:
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return parenthesize("group", e.expression)
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case Literal:
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if e.value == nil {
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return "nil"
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}
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return fmt.Sprintf("%v", e.value)
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case Unary:
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return parenthesize(e.operator.Lexeme, e.right)
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}
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return "ERROR: reached impossible branch in print function"
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}
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func parenthesize(name string, exprs ...Expr) string {
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var sb strings.Builder
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sb.WriteString("(" + name)
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for _, expr := range exprs {
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sb.WriteString(" ")
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sb.WriteString(print(expr))
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}
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sb.WriteString(")")
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return sb.String()
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}
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// This was briefly a testing function for the AST class at the end of ch. 5
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/*
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func main() {
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var expression Expr = Binary{
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Unary{
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lexer.NewToken(lexer.MINUS, "-", nil, 1),
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Literal{123},
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},
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lexer.NewToken(lexer.STAR, "*", nil, 1),
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Grouping{
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Literal{45.67},
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},
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}
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fmt.Println(print(expression))
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}
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*/
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