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103 lines
3.8 KiB
103 lines
3.8 KiB
/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef LIBTEXTCLASSIFIER_UTILS_GRAMMAR_PARSING_DERIVATION_H_
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#define LIBTEXTCLASSIFIER_UTILS_GRAMMAR_PARSING_DERIVATION_H_
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#include <vector>
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#include "utils/grammar/parsing/parse-tree.h"
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namespace libtextclassifier3::grammar {
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// A parse tree for a root rule.
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struct Derivation {
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const ParseTree* parse_tree;
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int64 rule_id;
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// Checks that all assertions are fulfilled.
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bool IsValid() const;
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int64 GetRuleId() const { return rule_id; }
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const ParseTree* GetParseTree() const { return parse_tree; }
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};
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// Deduplicates rule derivations by containing overlap.
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// The grammar system can output multiple candidates for optional parts.
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// For example if a rule has an optional suffix, we
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// will get two rule derivations when the suffix is present: one with and one
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// without the suffix. We therefore deduplicate by containing overlap, viz. from
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// two candidates we keep the longer one if it completely contains the shorter.
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// This factory function works with any type T that extends Derivation.
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template <typename T, typename std::enable_if<std::is_base_of<
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Derivation, T>::value>::type* = nullptr>
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// std::vector<T> DeduplicateDerivations(const std::vector<T>& derivations);
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std::vector<T> DeduplicateDerivations(const std::vector<T>& derivations) {
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std::vector<T> sorted_candidates = derivations;
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std::stable_sort(sorted_candidates.begin(), sorted_candidates.end(),
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[](const T& a, const T& b) {
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// Sort by id.
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if (a.GetRuleId() != b.GetRuleId()) {
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return a.GetRuleId() < b.GetRuleId();
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}
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// Sort by increasing start.
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if (a.GetParseTree()->codepoint_span.first !=
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b.GetParseTree()->codepoint_span.first) {
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return a.GetParseTree()->codepoint_span.first <
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b.GetParseTree()->codepoint_span.first;
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}
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// Sort by decreasing end.
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return a.GetParseTree()->codepoint_span.second >
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b.GetParseTree()->codepoint_span.second;
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});
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// Deduplicate by overlap.
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std::vector<T> result;
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for (int i = 0; i < sorted_candidates.size(); i++) {
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const T& candidate = sorted_candidates[i];
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bool eliminated = false;
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// Due to the sorting above, the candidate can only be completely
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// intersected by a match before it in the sorted order.
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for (int j = i - 1; j >= 0; j--) {
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if (sorted_candidates[j].rule_id != candidate.rule_id) {
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break;
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}
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if (sorted_candidates[j].parse_tree->codepoint_span.first <=
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candidate.parse_tree->codepoint_span.first &&
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sorted_candidates[j].parse_tree->codepoint_span.second >=
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candidate.parse_tree->codepoint_span.second) {
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eliminated = true;
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break;
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}
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}
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if (!eliminated) {
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result.push_back(candidate);
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}
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}
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return result;
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}
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// Deduplicates and validates rule derivations.
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std::vector<Derivation> ValidDeduplicatedDerivations(
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const std::vector<Derivation>& derivations);
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} // namespace libtextclassifier3::grammar
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#endif // LIBTEXTCLASSIFIER_UTILS_GRAMMAR_PARSING_DERIVATION_H_
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