Re: compare of 2 existing methods to implement grammar recursion

On 07/29/2016 10:31 AM, Larry Evans wrote:
> The repository:
>    https://github.com/boostorg/spirit/tree/develop
> has toy.cpp here:
>    */workbench/x3/toy/toy.cpp
> which connects the rule with it's rule_definition using
> the context; however, it's not clear from the code how
> to connect multiple rule's withe their rule_definition's.
>
> In contrast:
>
>    */include/boost/spirit/home/x3/nonterminal/rule.hpp
>
> uses the BOOST_SPIRIT_DEFINE macro to do this, as illustrated by:
>
>    */example/x3/calc/calc1.cpp
>
> The gist:
>
>    https://gist.github.com/cppljevans/3634cc4e8ad4da81531608e6aa847de5
>
> shows both methods except, in contrast to toy.cpp, it uses
> make_defns to link multiple rule's with their definitions.
>
> Also, the gist uses a macro, USE_PARSE_RULE, to switch between the
> 2 methods to ease comparison.

OOPS.  Apparently the 2 methods of linking a rule with it's
rule_definition can be used together.  The decision about which
to use is done by the BOOST_SPIRIT_DEFINE; hence, the above
rationale for USE_PARSE_RULE is not valid :(

Hence, replaced the USE_PARSE_RULE macro with USE_SPIRIT_DEFINE macro.
Comments under the macros should clarify their purpose.

Also, added the USE_MIXED_DEF to decide whether to use both
BOOST_SPIRIT_DEFINE *and* rule_defns to connect the rule's with
their rule_definition's.  The example output shows where
BOOST_SPIRIT_DEFINE was used to link expr and fact with their
rule_definition's, but where rule_defns was used to link
term with it's rule_definition.
[snip]



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