1 /* 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef LIBTEXTCLASSIFIER_UTILS_GRAMMAR_SEMANTICS_COMPOSER_H_ 18 #define LIBTEXTCLASSIFIER_UTILS_GRAMMAR_SEMANTICS_COMPOSER_H_ 19 20 #include <unordered_map> 21 #include <vector> 22 23 #include "utils/base/arena.h" 24 #include "utils/base/status.h" 25 #include "utils/base/statusor.h" 26 #include "utils/flatbuffers/flatbuffers.h" 27 #include "utils/grammar/parsing/derivation.h" 28 #include "utils/grammar/parsing/parse-tree.h" 29 #include "utils/grammar/semantics/eval-context.h" 30 #include "utils/grammar/semantics/evaluator.h" 31 #include "utils/grammar/semantics/expression_generated.h" 32 #include "utils/grammar/semantics/value.h" 33 #include "utils/grammar/text-context.h" 34 35 namespace libtextclassifier3::grammar { 36 37 // Semantic value composer. 38 // It evaluates a semantic expression of a syntactic parse tree as a semantic 39 // value. 40 // It evaluates the constituents of a rule match and applies them to semantic 41 // expression, calling out to semantic functions that implement the basic 42 // building blocks. 43 class SemanticComposer : public SemanticExpressionEvaluator { 44 public: 45 // Expects a flatbuffer schema that describes the possible result values of 46 // an evaluation. 47 explicit SemanticComposer(const reflection::Schema* semantic_values_schema); 48 49 // Evaluates a semantic expression that is associated with the root of a parse 50 // tree. 51 StatusOr<const SemanticValue*> Eval(const TextContext& text_context, 52 const Derivation& derivation, 53 UnsafeArena* arena) const; 54 55 // Applies a semantic expression to a list of constituents and 56 // produces an output semantic value. 57 StatusOr<const SemanticValue*> Apply(const EvalContext& context, 58 const SemanticExpression* expression, 59 UnsafeArena* arena) const override; 60 61 private: 62 // Evaluates a semantic expression against a parse tree. 63 StatusOr<const SemanticValue*> Eval(const TextContext& text_context, 64 const SemanticExpressionNode* derivation, 65 UnsafeArena* arena) const; 66 67 std::unordered_map<SemanticExpression_::Expression, 68 std::unique_ptr<SemanticExpressionEvaluator>> 69 evaluators_; 70 }; 71 72 } // namespace libtextclassifier3::grammar 73 74 #endif // LIBTEXTCLASSIFIER_UTILS_GRAMMAR_SEMANTICS_COMPOSER_H_ 75