[boost] [Range] contains() for unsorted ranges?

Hello, Wouldn't the library be well served by providing a contains() algorithm - with the same overloads/versions as find - for unsorted ranges? Surely, having to test against the range's end ruins the otherwise expressive syntax offered; especially when adaptors are involved and one has to test against the adapted range's end. Perhaps I am missing an obvious reason why not? Albert -- kojirion.github.io