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Finding the Next Smaller Representable Value (float_prior)

#include <boost/math/special_functions/next.hpp>
namespace boost{ namespace math{

template <class FPT>
FPT float_prior(FPT val);

}} // namespaces
Description - float_prior

Returns the next representable value which is less than x. If x is non-finite then returns the result of a domain_error. If there is no such value less than x then returns an overflow_error.

Has the same effect as

nextafter(val, -(std::numeric_limits<FPT>::max)());  // Note most negative value -max.