monitors is distributed under the Boost Software License, version 1.0. (See accompanying file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
monitors is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Boost Software License for more details.
Index returns the index of monitor in list from function All().
If monitor is not in list, the index of default monitor is returned.
At failure, -1 is returned.