utils/grammar/semantics/expression.fbs

// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

include "utils/flatbuffers/flatbuffers.fbs";

namespace libtextclassifier3.grammar.SemanticExpression_;
union Expression {
  ConstValueExpression,
  ConstituentExpression,
  ComposeExpression,
  SpanAsStringExpression,
  ParseNumberExpression,
  MergeValueExpression,
  ArithmeticExpression,
}

// A semantic expression.
namespace libtextclassifier3.grammar;
table SemanticExpression {
  expression:SemanticExpression_.Expression;
}

// A constant flatbuffer value.
namespace libtextclassifier3.grammar;
table ConstValueExpression {
  // The base type of the value.
  base_type:int;

  // The id of the type of the value.
  // The id is used for lookup in the semantic values type metadata.
  type:int;

  // The serialized value.
  value:[ubyte];
}

// The value of a rule constituent.
namespace libtextclassifier3.grammar;
table ConstituentExpression {
  // The id of the constituent.
  id:ushort;
}

// The fields to set.
namespace libtextclassifier3.grammar.ComposeExpression_;
table Field {
  // The field to set.
  path:libtextclassifier3.FlatbufferFieldPath;

  // The value.
  value:SemanticExpression;
}

// A combination: Compose a result from arguments.
// https://mitpress.mit.edu/sites/default/files/sicp/full-text/book/book-Z-H-4.html#%_toc_%_sec_1.1.1
namespace libtextclassifier3.grammar;
table ComposeExpression {
  // The id of the type of the result.
  type:int;

  fields:[ComposeExpression_.Field];
}

// Lifts a span as a value.
namespace libtextclassifier3.grammar;
table SpanAsStringExpression {
}

// Parses a string as a number.
namespace libtextclassifier3.grammar;
table ParseNumberExpression {
  // The base type of the value.
  base_type:int;

  value:SemanticExpression;
}

// Merge the semantic expressions.
namespace libtextclassifier3.grammar;
table MergeValueExpression {
  // The id of the type of the result.
  type:int;

  values:[SemanticExpression];
}

// The operator of the arithmetic expression.
namespace libtextclassifier3.grammar.ArithmeticExpression_;
enum Operator : int {
  NO_OP = 0,
  OP_ADD = 1,
  OP_MUL = 2,
  OP_MAX = 3,
  OP_MIN = 4,
}

// Simple arithmetic expression.
namespace libtextclassifier3.grammar;
table ArithmeticExpression {
  // The base type of the operation.
  base_type:int;

  op:ArithmeticExpression_.Operator;
  values:[SemanticExpression];
}