gettext: boost-format

 
 15.3.21 Boost Format Strings
 ----------------------------
 
    Boost format strings are described in the documentation of the
 ‘boost::format’ class, at
 <https://www.boost.org/libs/format/doc/format.html>.  In summary, a
 directive has either the same syntax as in a C format string, such as
 ‘%1$+5d’, or may be surrounded by vertical bars, such as ‘%|1$+5d|’ or
 ‘%|1$+5|’, or consists of just an argument number between percent signs,
 such as ‘%1%’.