lat.hpp

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#ifndef EDSP_LAT_HPP
#define EDSP_LAT_HPP

#include <algorithm>
#include <functional>
#include <cmath>

namespace edsp { namespace feature { inline namespace temporal {

    template <typename ForwardIt, typename Numeric>
    constexpr auto lat(ForwardIt first, ForwardIt last, Numeric samplerate,
            Numeric start_threshold, Numeric stop_threshold) {
        using value_type = typename std::iterator_traits<ForwardIt>::value_type;
        const auto max_value           = *std::max_element(first, last);
        const auto cutoff_start_attack = max_value * start_threshold;
        const auto cutoff_stop_attack  = max_value * stop_threshold;
        const auto start_iter = std::find_if(first, last,
                     std::bind(std::greater_equal<value_type>(), std::placeholders::_1, cutoff_start_attack));
        const auto stop_iter = std::find_if(first, last,
                     std::bind(std::greater_equal<value_type >(), std::placeholders::_1, cutoff_stop_attack));
        const auto start_attack = std::distance(first, start_iter);
        const auto stop_attack = std::distance(first, stop_iter);
        const auto attack_time = static_cast<value_type>(stop_attack - start_attack)
                / static_cast<value_type>(samplerate);
        constexpr auto threshold = static_cast<value_type >(10e-5);
        return (attack_time > threshold) ? static_cast<T>(std::log10(attack_time)) : -5;
    }
}}}

#endif //EDSP_LAT_HPP