format_dense_vector.h

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/*
 * Copyright 2022 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 <Eigen/Core>
#include <fmt/base.h>
 
#include "num_collect/base/exception.h"
#include "num_collect/base/precondition.h"
#include "num_collect/logging/logging_macros.h"
 
namespace num_collect::util {
 
namespace impl {
 
template <typename Vector>
class dense_vector_format_view {
public:
    explicit dense_vector_format_view(const Vector& vec) : vec_(&vec) {}
 
    [[nodiscard]] auto vec() const noexcept -> const Vector& { return *vec_; }
 
private:
    const Vector* vec_;
};
 
}  // namespace impl
 
template <typename Vector>
[[nodiscard]] inline auto format_dense_vector(
    const Eigen::DenseBase<Vector>& vec) {
    NUM_COLLECT_PRECONDITION(
        vec.cols() == 1, "format_dense_vector requires a vector.");
    return impl::dense_vector_format_view<Vector>(vec.derived());
}
 
}  // namespace num_collect::util
 
namespace fmt {
 
template <typename Vector>
struct formatter<num_collect::util::impl::dense_vector_format_view<Vector>>
    : public formatter<typename Vector::Scalar> {
public:
    auto format(
        const num_collect::util::impl::dense_vector_format_view<Vector>& val,
        format_context& context) const -> decltype(context.out()) {
        const auto& vec = val.vec();
        return format_impl(vec, context);
    }
 
private:
    auto format_impl(const Vector& vec, format_context& context) const
        -> decltype(context.out()) {
        const Eigen::Index size = vec.size();
        auto out = context.out();
        *out = '[';
        ++out;
        for (Eigen::Index i = 0; i < size; ++i) {
            if (i != 0) {
                out = write_comma(out);
            }
            context.advance_to(out);
            out = formatter<typename Vector::Scalar>::format(vec(i), context);
        }
        *out = ']';
        ++out;
        return out;
    }
 
    static auto write_comma(format_context::iterator out)
        -> format_context::iterator {
        *out = ',';
        ++out;
        *out = ' ';
        ++out;
        return out;
    }
};
 
}  // namespace fmt