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namespace traditional

{

int bits_of(int remain)

{

if (remain)

return 1+bits_of( remain>>1 );

return 0;

}

int bits_of(void)

{

return bits_of(~(int)0);

}

}

namespace modern

{

template<int,typename THEN, typename ELSE>

struct IF { typedefTHEN type; };

template<typename THEN, typename ELSE>

struct IF<0,THEN,ELSE> { typedef ELSE type; };

template<typename T, T X>

struct zero

{

static const Tvalue = X;

};

template<typename T, T X>

struct bits_of

{

typedef typenameIF<X, bits_of<T,(X>>1)>, zero<T,0> >::type type;

static const Tvalue = type::value + !!X;

};

}

typedef int a0[bits_of<int,0>::value==0? 1: -1];
typedef int a1[bits_of<int,1>::value==1? 1: -1];
typedef int a2[bits_of<int,2>::value==2? 1: -1];
typedef int a3[bits_of<int,3>::value==2? 1: -1];
typedef int a4[bits_of<int,4>::value==3? 1: -1];
typedef int a7[bits_of<int,7>::value==3? 1: -1];
typedef int a8[bits_of<int,8>::value==4? 1: -1];
typedef int a15[bits_of<int,15>::value==4? 1: -1];
typedef int a16[bits_of<int,16>::value==5? 1: -1];

namespace third_party

{

// 您确定您能看懂？  

}