[boost] Re: Spirit and slow compile (from gmane.comp.lib.boost.devel)

From: Hartmut Kaiser (hartmutkaiser_at_[hidden])
Date: 2003-01-15 12:10:44

Sorry, I've missed an important detail (see below):

> Vincent Finn wrote:
>
> > >>I was talking to you on the boost newsgroup about spirit
> > being slow to
> > >>compile Here is a standalone section of code, it'll
> compile but you
> > >>can't do anything with it The compile takes about 15 mins on my
> > >>machine (We are using spirit for a second file but that is
> > smaller and
> > >>only takes a minute or two)
> [snip]
>
> > I'll give it a go :-)
>
> There is something you can do additionally, I think.
>
> The large compile times result from the tight coupling of all
> your Spirit grammars, so that these couldn't be compiled
> separately (as far as I understood it). To overcome this
> problem you have to decouple the use of a grammar from it's
> instantiation. I've solved this through a small helper
> generator template function like the following:
>
>     //  parse the grammar and return the resulting parse tree
>     template <typename IteratorT>
>     boost::spirit::parse_info<IteratorT>
>     parse_grammar (IteratorT const &first, IteratorT const &last);
>
> This declaration you should make visible to the code, which
> _uses_ the grammar. There you have to replace your call to
>
>     boost::spirit::parse(first, last) --> parse_grammar(first, last);

This should read
    your_grammar g;
    boost::spirit::parse(first, last, g) --> parse_grammar(first, last);
>
> The definition of the function parse_grammar has to look like
> the following
>
>     template <typename IteratorT>
>     boost::spirit::parse_info<IteratorT>
>     parse_grammar (IteratorT const &first, IteratorT const &last)
>     {
>         return boost::spirit::parse(first, last);

This should read:
        your_grammar g;
        return boost::spirit::parse(first, last, g);

This way the declaration of your_grammar have to be included only in the
second compilation unit.

>     }
>
> and this definition you can put into a separate compilation
> unit. The only problem left is, that you have to instantiate
> the correct parse_grammar function explicitely with the
> iterator type, you've used, maybe like the following:
>
>     template boost::spirit::parse_info<char const *>
>     parse_grammar (char const * const &first, char const *
> const &last);
>
> Certainly this explicit instantiation should go into the
> second compilation unit. Hope this helps.
>
> Regards Hartmut
>
> BTW this method works well for me already in the ongoing
> Spirit based C preprocessor sample.

Sorry for the noise.

Regards Hartmut