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@ -11,7 +11,7 @@ import (
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const CONCAT rune = '~'
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func isOperator(c rune) bool {
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if c == '+' || c == '*' || c == '|' || c == CONCAT {
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if c == '+' || c == '?' || c == '*' || c == '|' || c == CONCAT {
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return true
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}
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return false
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@ -19,7 +19,7 @@ func isOperator(c rune) bool {
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/* priority returns the priority of the given operator */
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func priority(op rune) int {
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precedence := []rune{'|', CONCAT, '+', '*'}
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precedence := []rune{'|', CONCAT, '+', '*', '?'}
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return slices.Index(precedence, op)
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}
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@ -43,7 +43,7 @@ func shuntingYard(re string) string {
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re_postfix = append(re_postfix, re_runes[i])
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if re_runes[i] != '(' && re_runes[i] != '|' {
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if i < len(re_runes)-1 {
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if re_runes[i+1] != '|' && re_runes[i+1] != '*' && re_runes[i+1] != '+' && re_runes[i+1] != ')' {
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if re_runes[i+1] != '|' && re_runes[i+1] != '*' && re_runes[i+1] != '+' && re_runes[i+1] != '?' && re_runes[i+1] != ')' {
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re_postfix = append(re_postfix, CONCAT)
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}
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}
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@ -153,6 +153,15 @@ func thompson(re string) *State {
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s2 := kleene(*s1)
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s1 = concatenate(s1, s2)
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nfa = append(nfa, s1)
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case '?': // ab? is equivalent to a(b|)
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s1 := mustPop(&nfa)
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s2 := &State{}
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s2.transitions = make(map[int][]*State)
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s2.content = EPSILON
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s2.output = make([]*State, 0)
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s2.isEmpty = true
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s3 := alternate(s1, s2)
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nfa = append(nfa, s3)
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case '|':
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s1 := mustPop(&nfa)
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s2 := mustPop(&nfa)
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