Re: simple sql query parser

On 01/01/2018 01:43 PM, labsquare wrote:
> It works perfect !!! Thanks you !
> My last question : what's the goal of "class" inside the rule declaration .
> 
> auto rule = x3::rule<*class whereRule*, string>()
> 
> is "class whereRule" is really necessary ? What's the purpose ?
> 
[snip]
It's used here:

https://github.com/boostorg/spirit/blob/develop/include/boost/spirit/home/x3/nonterminal/rule.hpp#L32

What that does is looks up the rule definition in the context arg to the 
function *IF* BOOST_SPIRIT_DEFINE has *not* been used to associate the
rule<ID,...> with it's RHS.

OTOH, *IF* BOOST_SPIRIT_DEFINE *has* been used, then that creates
another parse_rule function specialized on thate rule<ID,...>; hence,
that specialized parse_rule is called instead.  The parse_rule function
is called from within the rule<ID,...>::parse function here:

https://github.com/boostorg/spirit/blob/develop/include/boost/spirit/home/x3/nonterminal/rule.hpp#L113

Like me, you might find that a little hard to follow, but that's my
understanding of how it works.

HTH.

-regards,
Larry






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