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package main
type RegexState interface {
eat(char rune) []RegexState
accepting() bool
}
type RegexNoneState struct {}
func (state RegexNoneState) eat(char rune) []RegexState {
return nil
}
func (state RegexNoneState) accepting() bool {
return true
}
type RegexAnyState struct {
next RegexState
}
func (state RegexAnyState) eat(char rune) []RegexState {
return []RegexState{state.next}
}
func (state RegexAnyState) accepting() bool {
return false
}
type RegexRuneState struct {
rune rune
next RegexState
}
func (state RegexRuneState) eat(char rune) []RegexState {
if char == state.rune {
return []RegexState{state.next}
}
return nil
}
func (state RegexRuneState) accepting() bool {
return false
}
type RegexGroupState struct {
first, second RegexState
}
func (state RegexGroupState) eat(char rune) []RegexState {
return append(state.first.eat(char), state.second.eat(char)...)
}
func (state RegexGroupState) accepting() bool {
return state.first.accepting() || state.second.accepting()
}
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