template<
      typename C
    , typename T1
    , typename T2
    >
struct[if\_](./if.html){
    typedef_unspecified_type;
};

#include <[boost/mpl/if.hpp](../../../../boost/mpl/if.hpp)>

typedef[if\_](./if.html)<c,t1,t2>::type t;

typedef[if\_](./if.html)<[true\_](./bool.html),char,long>::type t1;
typedef[if\_](./if.html)<[false\_](./bool.html),char,long>::type t2;[BOOST\_MPL\_ASSERT](./assert.html)(( is_same<t1, char> ));[BOOST\_MPL\_ASSERT](./assert.html)(( is_same<t2, long> ));

// allocates space for an object of class T on heap or "inplace"
// depending on its[size](./size.html)template< typename T > struct lightweight
{
    // ...
    typedef typename[if\_](./if.html)<[less\_equal](./less-equal.html)<[sizeof\_](./sizeof.html)<T>,[sizeof\_](./sizeof.html)<T*> >
        , inplace_storage<T>
        , heap_storage<T>
        >::type impl_t;

    impl_t impl;
};