Re: [boost] [variant] match()

Le 07/01/15 09:41, Eelis a écrit :

Boost.Variant provides access through get() and visitors, but in C++11 we can do so much better! :)

For a boost::variant, the attached small utility function match() lets you write:

match(v, [](A & a){ cout << "it's a A!"; } [](B & b){ cout << "oh, a B!"; } [](C & c){ cout << "ah yes, a C!"; });

Return values are supported. I think this really belongs in Boost. It makes variants much more usable.

Regards,

Eelis

P.S. I have not attempted a C++98 implementation.

P.S.2. Right after finishing my implementation, I discovered another, /vastly/ more complex implementation of the same thing:

https://github.com/exclipy/inline_variant_visitor

I'm not sure its complexity gives that implementation any advantages. Hi,

IIUC the code, your implementation has some limitations as the user must provide a function for each variant type and in the same order. There is another one here [1] based on the overload function as defined here [2]. There are some examples test here [3]. The same function can be used for optional/expected/any and many more sum types (even if any is not a sum type, the selection of some possible types makes it posible to see this selection as a sum type). Best, Vicente [1] https://github.com/viboes/tags/blob/master/include/yafpl/v1/functional/match... [2] https://github.com/viboes/tags/blob/master/include/yafpl/v1/functional/overl... [3] https://github.com/viboes/tags/blob/master/test/variant/include_pass.cpp