Re: Spirit X3 employee.cpp compile error

On 08/20/2016 08:30 AM, Larry Evans wrote:
[snip]

> OOPS.  I should have re-looked at:
>
> https://github.com/boostorg/spirit/blob/develop/workbench/x3/toy/toy.cpp#L134
>
> which shows the rule_definition<>::parse function stores the
> rule definition in the context dictionary.  Then, even
> when BOOST_SPIRIT_DEFINE is not used, the rule rhs is looked up
> by the rule<...>::parse function:
>
> https://github.com/boostorg/spirit/blob/develop/workbench/x3/toy/toy.cpp#L154
>
> The process is a little more complicated in the actual code.
> There, rule_defintion<...>::parse:
>
> https://github.com/boostorg/spirit/blob/master/include/boost/spirit/home/x3/nonterminal/rule.hpp#L64
>
> *maybe* does something similar by putting the definition in the
> context dictionary where the key is the rule ID.
Yep, it's done here:

https://github.com/boostorg/spirit/blob/master/include/boost/spirit/home/x3/nonterminal/detail/rule.hpp#L209

in the expression:

   make_rule_context<ID>(rhs, context, is_default_parse_rule())

which, in case BOOST_SPIRIT_DEFINE is not used to define the rule,
and the rule definition is not already in the context, calls:

https://github.com/boostorg/spirit/blob/master/include/boost/spirit/home/x3/support/context.hpp#L89

However, this only happens if rule_definition's on on the RHS of rules,
as done here:

http://coliru.stacked-crooked.com/a/41425cb30e49bc8a

in lines 29-39 where process, node, and node_map are all rule_definition's.

However, this use of rule_definitions on the RHS or rules suffers the
same "crazy long mangled names" problem mentioned by Tongari here:

http://boost.2283326.n4.nabble.com/compare-of-2-existing-methods-to-implement-grammar-recursion-tt4687574.html#a4687690

So why wouldn't the simpler rule_map solution be preferred?  With
rule_map, there's no need to put rule_definitions on RHS, there's
only the need to create the rule_map once and pass that as part
of the context.

-regards,
Larry



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