boost::algorithm::all_of
// In header: <boost/algorithm/cxx11/all_of.hpp> template<typename Range, typename Predicate> BOOST_CXX14_CONSTEXPR bool all_of(const Range & r, Predicate p);
returns true on an empty range
Parameters:
r
The input range
p
A predicate for testing the elements of the range
Returns:
true if all elements in the range satisfy the predicate 'p'