Trouble implementing the equivalent of boost::mpl::or_

JUAN DENT (326)
Hi,

As an exercise, I am trying to implement boost::mpl::or_ calling it logical_or. I have suceeded by using mpl::eval_if but have not been able to do it using mpl::if_. Following code shows my correct implementation and my attempt to use mpl::if_:

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namespace mpl = boost::mpl;

template<typename N1, typename N2>
	struct logical_or  : mpl::bool_<
		mpl::eval_if<
			N1,
			mpl::true_,
		mpl::eval_if<
			N2,
			mpl::true_,
			mpl::false_>
		>::type::value
	>
	{};

namespace Using_if_
{
		template<typename N1, typename N2>
		struct logical_or : mpl::bool_<
			mpl::if_<
			N1,
			mpl::true_,
			mpl::if_<
			N2,
			mpl::true_,
			mpl::false_>
			>::value
		>
		{};

}


I am trying to retain short-circuit behavior as that given by mpl::or_.

Any help greatly appreciated!!

Juan Dent

I found the solution!! Place an extra type at the end of the first mpl::if_ as follows:

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	namespace Using_if_
	{
		template<typename N1, typename N2>
		struct logical_or : mpl::bool_<
			mpl::if_<
			N1,
			mpl::true_,
			mpl::if_<
			N2,
			mpl::true_,
			mpl::false_>
			>::type::type::value
		>
		{};

	}


Just putting it in writing cleared my mind!!
Eureka!

Regards,
Juan Dent
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