expression.h

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/*
 * Copyright 2026 MusicScience37 (Kenta Kabashima)
 *
 * 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
 *
 *     http://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.
 */
#pragma once
 
#include <variant>
 
#include <fmt/base.h>
 
#include "func_sketch/expressions/binary_expression.h"
#include "func_sketch/expressions/constant_expression.h"
#include "func_sketch/expressions/expression_decl.h"  // IWYU pragma: keep
#include "func_sketch/expressions/function_call_expression.h"
#include "func_sketch/expressions/parameter_expression.h"
#include "func_sketch/expressions/unary_expression.h"
 
namespace func_sketch::expressions {

class Expression {
public:
    using VariantType = std::variant<ConstantExpression, ParameterExpression,
        UnaryExpression, BinaryExpression, FunctionCallExpression>;

    explicit Expression(ConstantExpression expression)
        : expression_(expression) {}

    explicit Expression(ParameterExpression expression)
        : expression_(expression) {}

    explicit Expression(UnaryExpression expression) : expression_(expression) {}

    explicit Expression(BinaryExpression expression)
        : expression_(expression) {}

    explicit Expression(FunctionCallExpression expression)
        : expression_(expression) {}

    template <typename T>
    [[nodiscard]] const T& as() const {
        return std::get<T>(expression_);
    }

    [[nodiscard]] const VariantType& as_variant() const { return expression_; }
 
private:
    VariantType expression_;
};
 
}  // namespace func_sketch::expressions

template <>
struct fmt::formatter<func_sketch::expressions::Expression>
    : fmt::formatter<string_view> {
    auto format(const func_sketch::expressions::Expression& value,
        format_context& context) const -> format_context::iterator;
};

template <>
struct fmt::formatter<func_sketch::expressions::Expression*>
    : fmt::formatter<string_view> {
    auto format(const func_sketch::expressions::Expression* value,
        format_context& context) const -> format_context::iterator;
};