The MPL Reference Manual: BOOST_MPL_LIMIT_MAP_SIZE

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# BOOST_MPL_LIMIT_MAP_SIZE

### Synopsis

    #if !defined(BOOST_MPL_LIMIT_MAP_SIZE)
    #   define BOOST_MPL_LIMIT_MAP_SIZE \
            implementation-defined integral constant \
    /**/
    #endif

### Description

`BOOST_MPL_LIMIT_MAP_SIZE` is an overridable configuration macro regulating the maximum arity of the `map`'s variadic form. In this implementation of the library, `BOOST_MPL_LIMIT_MAP_SIZE` has a default value of 20. To override the default limit, define `BOOST_MPL_LIMIT_MAP_SIZE` to the desired maximum arity rounded up to the nearest multiple of ten before including any library header. [Note: Overriding will take effect only if the library is configured not to use preprocessed headers. See `BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS` for more information. — end note]

### Example

    #define BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
    #define BOOST_MPL_LIMIT_MAP_SIZE 10
    #include <boost/mpl/map.hpp>
    #include <boost/mpl/pair.hpp>
    #include <boost/mpl/int.hpp>

    using namespace boost::mpl;

    template< int i > struct ints : pair< int_<i>,int_<i> > {};

    typedef map< ints<1> > m_1;
    typedef map< ints<1>, ints<2>, ints<3>, ints<4>, ints<5>
        ints<6>, ints<7>, ints<8>, ints<9>, ints<10> > m_10;

    // typedef map< ints<1>, ints<2>, ints<3>, ints<4>, ints<5>
    //     ints<6>, ints<7>, ints<8>, ints<9>, ints<10>, ints<11> > m_11; // error!

### See also

Configuration, `BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS`, `BOOST_MPL_LIMIT_SET_SIZE`