Performance timer in pure C++11

perf_timer.h

#include <chrono>
#include <type_traits>

// Floating seconds duration
using fseconds = std::chrono::duration<double>;

class PerfTimer
{
public:
    using clock = std::conditional<
        std::chrono::high_resolution_clock::is_steady,
        std::chrono::high_resolution_clock,
        std::chrono::steady_clock
    >::type;

    PerfTimer(): m_start(clock::now()) {}

    fseconds passed() const { return clock::now() - m_start; }

private:
    clock::time_point m_start;
};

// Usage example
void test()
{
    PerfTimer timer;
    ... // Time measured piece of code
    auto time_spent = timer.passed();
    std::cout << "Time spent, seconds: " << time_spent.count();
}