boost::mpl学习日记1

记录一下mpl学习结果：

引用

1-1.
    Turn vector_c<int,1,2,3> into a type sequence with elements (2,3,4) using transform.

对vector做一个加1就可以了

	
typedef mpl::vector_c<int,1,2,3>	AAA;
typedef mpl::vector_c<int,2,3,4>	CCC;
typedef mpl::transform<AAA,mpl::plus<_1, mpl::int_<1> > >::type BBB;
BOOST_STATIC_ASSERT((
	mpl::equal<BBB,CCC>::type::value
	));

引用

1-2.
    Turn vector_c<int,1,2,3> into a type sequence with elements (1,4,9) using transform.

对两个AAA相乘

typedef mpl::vector_c<int,1,4,9>	DDD;

typedef mpl::transform<AAA,AAA, mpl::multiplies<_1,_2>  >::type EEE;
BOOST_STATIC_ASSERT((
	mpl::equal<DDD,EEE>::type::value
	));

引用

1-5.

    There's still a problem with the dimensional analysis code in section 1.1. Hint: What happens when you do:

    f = f + m * a;

    Repair this example using techniques shown in this chapter.

加法操作支持两种类型，然后确保类型是一致的就可以了

template <class T, class D1, class D2>
quantity<T,D1>
operator+(quantity<T,D1> x, quantity<T,D2> y)
{
	BOOST_STATIC_ASSERT((
		mpl::equal<D1,D2>::type::value
		));
	return quantity<T,D1>(x.value() + y.value());
}