boost/math/tools/minima.hpp pass functor by ref

[ch816772@…]

Would it be better to pass the functor f by ref for the following

template <class F, class T> std::pair<T, T> brent_find_minima(F f, T min, T max, int bits);

template <class F, class T> std::pair<T, T> brent_find_minima(F f, T min, T max, int bits, boost::uintmax_t& max_iter);

To instead be:

template <class F, class T> std::pair<T, T> brent_find_minima(F& f, T min, T max, int bits);

template <class F, class T> std::pair<T, T> brent_find_minima(F& f, T min, T max, int bits, boost::uintmax_t& max_iter);