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53 lines
1.6 KiB
Go
53 lines
1.6 KiB
Go
package main
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// match tries to match the regex represented by given start-state, with
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// the given string
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func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
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currentStates := make([]*State, 0)
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tempStates := make([]*State, 0) // Used to store states that should be used in next loop iteration
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i := 0 // Index in string
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// Increment until we hit a character matching the start state
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if start.isEmpty == false {
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for int(str[i]) != start.content {
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i++
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}
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}
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currentStates = append(currentStates, start)
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startIdx = i
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i++ // Advance to next character so that we can check for transitions
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// Main loop
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for i < len(str) {
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// If there are any 0-transitions, take those
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// TODO: Maybe I need to keep taking 0-transitions until I don't have anymore. Needs to be tested
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for _, state := range currentStates {
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if len(state.transitions[EPSILON]) > 0 {
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tempStates = append(tempStates, state.transitions[EPSILON]...)
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}
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}
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copy(currentStates, tempStates)
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tempStates = nil
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// Take any transitions corresponding to current character
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for _, state := range currentStates {
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if len(state.transitions[int(str[i])]) > 0 {
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tempStates = append(tempStates, state.transitions[int(str[i])]...)
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}
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}
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copy(currentStates, tempStates)
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tempStates = nil
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// If any of the current-states is a last state, return true.
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for _, state := range currentStates {
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if state.isLast {
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endIdx = i
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return startIdx, endIdx, true
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}
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}
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i++
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}
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// We don't seem to have reached a last-state. Return fals
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return -1, -1, false
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}
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