ceph/src/boost/libs/range/doc/reference/adaptors/map_keys.qbk

   1 [/
   2     Copyright 2010 Neil Groves
   3     Distributed under the Boost Software License, Version 1.0.
   4     (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5 /]
   6 [section:map_keys map_keys]
   7
   8 [table
   9     [[Syntax] [Code]]
  10     [[Pipe] [`rng | boost::adaptors::map_keys`]]
  11     [[Function] [`boost::adaptors::keys(rng)`]]
  12 ]
  13
  14 * [*Precondition:] The `value_type` of the range is an instantiation of `std::pair`.
  15 * [*Postcondition:] For all elements `x` in the returned range, `x` is the result of `y.first` where `y` is the corresponding element in the original range.
  16 * [*Range Category:] __single_pass_range__
  17 * [*Range Return Type:] `boost::select_first_range<decltype(rng)>`
  18 * [*Returned Range Category:] The range category of `rng`.
  19
  20 [section:map_keys_example map_keys example]
  21 [import ../../../test/adaptor_test/map_keys_example.cpp]
  22 [map_keys_example]
  23 [endsect]
  24
  25 This would produce the output:
  26 ``
  27 0,1,2,3,4,5,6,7,8,9,
  28 ``
  29 [endsect]
  30
  31