Re: [boost] [variant] Warning: variadic templates in boost::variant

On Wed, Dec 11, 2013 at 8:30 AM, Steven Watanabe wrote:

AMDG

On 12/10/2013 06:57 PM, Andrey Semashev wrote:

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On Tuesday 10 December 2013 23:13:32 Peter Dimov wrote:

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template< typename T0 = blank, typename... TN > class variant;

Mapping variant<> to variant<blank> is not a good idea in principle. This has the potential of creating endless loops in generic code that takes variant and recursively calls itself with variant.

But such code is currently not valid, it should end the recursion at variant<T>. This doesn't change after the default is added.

So, anyone writing such a loop has to treat variant<> as a special case. That doesn't seem like the greatest idea.

Ok, we can allow variant<> in recursion but still make it act like variant<blank>.