52 lines
944 B
Go
52 lines
944 B
Go
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package expression
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import (
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"go/scanner"
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"go/token"
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)
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type Evaluator struct {
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operators map[token.Token]Operator
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functions map[string]func(stack *Stack) error
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}
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func New() *Evaluator {
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return &Evaluator{
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operators: DefaultOperators,
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functions: DefaultFunctions,
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}
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}
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func (e *Evaluator) Eval(expression string) (any, error) {
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s := scanner.Scanner{}
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fset := token.NewFileSet()
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file := fset.AddFile("", fset.Base(), len(expression))
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s.Init(file, []byte(expression), nil, scanner.ScanComments)
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tokens := make(chan Token)
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go func() {
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for {
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pos, tok, lit := s.Scan()
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if tok == token.SEMICOLON {
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continue
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}
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if tok == token.EOF {
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break
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}
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tokens <- Token{
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Token: tok,
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Literal: lit,
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Pos: int(pos),
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}
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}
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close(tokens)
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}()
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rpnTokens := e.ToPRN(tokens)
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return e.execute(rpnTokens)
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}
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type Operator struct {
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fn func(stack *Stack) error
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priority int
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isLeftAssoc bool
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}
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