mirror of https://github.com/mikefarah/yq.git
61 lines
2.0 KiB
Go
61 lines
2.0 KiB
Go
package treeops
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import (
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"errors"
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)
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type PathPostFixer interface {
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ConvertToPostfix([]*Token) ([]*PathElement, error)
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}
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type pathPostFixer struct {
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}
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func NewPathPostFixer() PathPostFixer {
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return &pathPostFixer{}
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}
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func popOpToResult(opStack []*Token, result []*PathElement) ([]*Token, []*PathElement) {
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var operatorToPushToPostFix *Token
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opStack, operatorToPushToPostFix = opStack[0:len(opStack)-1], opStack[len(opStack)-1]
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var pathElement = PathElement{PathElementType: Operation, OperationType: operatorToPushToPostFix.OperationType}
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return opStack, append(result, &pathElement)
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}
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func (p *pathPostFixer) ConvertToPostfix(infixTokens []*Token) ([]*PathElement, error) {
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var result []*PathElement
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// surround the whole thing with quotes
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var opStack = []*Token{&Token{PathElementType: OpenBracket, OperationType: None}}
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var tokens = append(infixTokens, &Token{PathElementType: CloseBracket, OperationType: None})
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for _, token := range tokens {
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switch token.PathElementType {
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case PathKey, ArrayIndex, SelfReference:
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var pathElement = PathElement{PathElementType: token.PathElementType, Value: token.Value, StringValue: token.StringValue}
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result = append(result, &pathElement)
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case OpenBracket:
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opStack = append(opStack, token)
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case CloseBracket:
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for len(opStack) > 0 && opStack[len(opStack)-1].PathElementType != OpenBracket {
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opStack, result = popOpToResult(opStack, result)
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}
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if len(opStack) == 0 {
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return nil, errors.New("Bad path expression, got close brackets without matching opening bracket")
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}
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// now we should have ( as the last element on the opStack, get rid of it
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opStack = opStack[0 : len(opStack)-1]
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default:
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var currentPrecedence = token.OperationType.Precedence
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// pop off higher precedent operators onto the result
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for len(opStack) > 0 && opStack[len(opStack)-1].OperationType.Precedence >= currentPrecedence {
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opStack, result = popOpToResult(opStack, result)
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}
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// add this operator to the opStack
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opStack = append(opStack, token)
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}
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}
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return result, nil
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}
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