Re: Spirit X3 employee.cpp compile error

On 08/12/2016 09:19 AM, Vincent Virgilio wrote:
>
>
>> On Aug 12, 2016, at 9:29 AM, Larry Evans <[email protected]> wrote:
>>
>>> On 08/12/2016 07:53 AM, Vincent Virgilio wrote:
>>>
>>>
>>>> On Aug 12, 2016, at 08:27 AM, Larry Evans <[email protected]> wrote:
>>>>
>>>>> On 08/12/2016 06:40 AM, Larry Evans wrote:
>>>>> [snip]
>>>>>
>>>>>> GitHub: [email protected] <mailto:[email protected]>:boostorg/spirit.git
>>>>>>
>>>>>> Use the develop branch.
>>>>>> --}--cut here--
>>>>> The 2 template arg rule code is actually in the x3-devel branch instead
>>>>> of the develop branch:
>>>>>
>>>>> https://github.com/boostorg/spirit/blob/x3-devel/include/boost/spirit/home/x3/nonterminal/rule.hpp#L80
>>>> [snip]
>>>> However, if you decide to use x3-devel, then the employee.cpp code
>>>> referenced in your OP needs to be modified so that the arguments
>>>> to BOOST_SPIRIT_DEFINE contain assignments instead of just
>>>> rule names. For example, see:
>>>>
>>>> https://github.com/boostorg/spirit/blob/x3-devel/example/x3/calc4.cpp#L218
>>>>
>>>> HTH.
>>>>
>>>> -regards,
>>>> Larry
>>>
>>> Hi Larry,
>>>
>>> Thanks for all the help so far.
>>>
>>> Why is BOOST_SPIRIT_DEFINE required if the rule declarations and
>>> definitions are already associated via assignment? In another small
>>> project, I was able to parse with an X3 grammar without that macro. In
>>> that case, very schematically, I had "auto const rule_name = rule<...>()
>>> = rule_def;"
>> [snip]
>> Hi Vincent,
>>
>> I can only guess that the grammar in this small project had no
>> recursive rules like the calc4.cpp grammar I mentioned above.
>>
>> That's only a guess; however, I *think* the whole purpose of
>> BOOST_SPIRIT_DEFINE is to allow mutually recursive rules, such as
>> that in calc4.cpp, *and* to avoid massive template names.
>> At least that's the conclusion I reach after reading
>> [email protected] reply to me here:
>>
>> https://sourceforge.net/p/spirit/mailman/message/35271675/
>>
>> HTH.
>>
>> -regards,
>> Larry
>
> Yes, the grammar was tiny.
>
> I think I see what you're saying.

Great!

The following gist:

https://gist.github.com/cppljevans/3d3bec54be8f3d0c4d8b94af84a6e529

hopefully will make things more clear.
It shows a grammar without recursion and one with.
There's also a macro, USE_DEFINE, which, if !defined(USE_DEFINE),
causes a compile error something like:

define.o
toy_why_define.cpp:132:9: error: static_assert failed 
"BOOST_SPIRIT_DEFINE undefined for this rule."
 
static_assert(!boost::is_same<get_type,undefined>::value,"BOOST_SPIRIT_DEFINE 
undefined for this rule.");
         ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

OTOH, when defined(USE_DEFINE), it runs without error.
The comments above the #define USE_SPIRIT_DEFINE try to explain
how it works.

HTH.

-regards,
Larry




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