Boost C++ Libraries: Ticket #12085: (a - b) === (!b >> a) does not hold in X3

Joel de Guzman — Sun, 27 Mar 2016 10:49:42 GMT

Is this a TST issue?

mikhail.strelnikov@… — Sun, 27 Mar 2016 13:46:21 GMT

Yes. What do you think about https://github.com/boostorg/spirit/pull/181/commits/1f6d6c61849e89527c9b7be0818a16ce4833e8cf ? Should this work in x3 or should it not in qi?

Joel de Guzman — Sun, 27 Mar 2016 22:22:56 GMT

I'm not sure. I still need to investigate. That said, if this one is a TST issue, then the test should be minimized further. It will be confusing to conflate the TST issue and the (!b >> a) and (a - b) issue together.

mikhail.strelnikov@… — Mon, 28 Mar 2016 16:48:08 GMT

I think all this can be minimized to -

static_assert(traits::is_substitute<fusion::deque<char, std::string>, std::string>::value == 1, "");

or even simpler

static_assert(traits::is_substitute<char, std::string>::value == 1, "");

Which is kind of makes sense - if we have a char, we can put it to a string.

If this compiles, then test passes. I've tried this by adding specialization

template <typename T, typename Attribute>
    struct is_substitute<T, Attribute, typename enable_if<is_container<Attribute> >::type>
        : is_substitute<typename mpl::eval_if
            <
                fusion::traits::is_sequence<T>,
                fusion::result_of::front<T>,
                mpl::identity<T>
            >::type, typename container_value<Attribute>::type> {};

Joel de Guzman — Mon, 28 Mar 2016 22:29:41 GMT

So it's not a TST issue then. An is_substitute specialization would be easy to add.

Joel de Guzman — Mon, 28 Mar 2016 22:31:29 GMT

Replying to djowel:

So it's not a TST issue then. An is_substitute specialization would be easy to add. Does your specialization compile? Seems too complicated.

Sun, 25 Feb 2018 01:12:45 GMT

I think have a good fix https://github.com/boostorg/spirit/pull/370

Thu, 01 Mar 2018 10:45:53 GMT

Fixed in https://github.com/boostorg/spirit/pull/370

status changed; resolution set

Joel de Guzman — Thu, 15 Mar 2018 22:58:57 GMT

status new → closed
resolution → fixed