boost::algorithm::one_of_equal
// In header: <boost/algorithm/cxx11/one_of.hpp> template<typename InputIterator, typename V> bool one_of_equal(InputIterator first, InputIterator last, const V & val);
Parameters:
first
The start of the input sequence
last
One past the end of the input sequence
val
A value to compare against
Returns:
true if the value 'val' exists only once in [first, last).