Subject: Re: [Boost-users] [spirit] help parsing data file into a struct
From: Kenny Riddile (kfriddile_at_[hidden])
Date: 2009-12-18 09:55:41
OvermindDL1 wrote:
> On Thu, Dec 17, 2009 at 11:44 AM, Kenny Riddile <kfriddile_at_[hidden]> wrote:
>> This is my first time using Spirit and I haven't messed with writing EBNF
>> grammars since college, so I'm sorry if this is a simple question. Lets say
>> I have a structure that looks like this:
>>
>> struct Foo
>> {
>> std::string someString;
>> std::string someOtherString;
>> std::vector<std::string> stringList;
>> };
>>
>> BOOST_FUSION_ADAPT_STRUCT(
>> Foo,
>> (std::string, someString)
>> (std::string, someOtherString)
>> (std::vector<std::string>, stringList) )
>>
>> and I have a data file that looks like this:
>>
>> SOMESTRING hello
>> SOMEOTHERSTRING goodbye
>>
>> STRINGLIST
>> {
>> string1
>> string2
>> string3
>> }
>>
>> I have written the following grammar to parse such a file into the struct
>> above:
>>
>> template< typename Iterator >
>> struct FooDefinition : spirit::qi::grammar< Iterator, Foo() >
>> {
>> FooDefinition()
>> : FooDefinition::base_type( start )
>> {
>> using namespace spirit::qi;
>>
>> start = someString >> +space >> someOtherString >> +space >>
>> stringList;
>> someString = lit("SOMESTRING") >> +space >> value;
>> someOtherString = lit("SOMEOTHERSTRING") >> +space >> value;
>> stringList = lit("STRINGLIST") >> *space >> lit('{') >> *space >>
>> (value % +space) >> *space >> lit('}');
>> value = +char_("a-zA-Z_0-9");
>> space = lit(' ') | lit('\n') | lit('\t');
>> }
>>
>> spirit::qi::rule< Iterator, Foo() > start;
>> spirit::qi::rule< Iterator, std::string() > someString;
>> spirit::qi::rule< Iterator, std::string() > someOtherString;
>> spirit::qi::rule< Iterator, std::vector<std::string>() > stringList;
>> spirit::qi::rule< Iterator, std::string() > value;
>> spirit::qi::rule< Iterator > space;
>> };
>>
>> However, I would like the order of the three statements in the data file
>> (SOMESTRING, SOMEOTHERSTRING, and STRINGLIST) to be irrelevant. Right now,
>> they must be in the order shown above for parsing to succeed. How would I
>> go about accomplishing this with Spirit?
>
> That is what the permutation operator is for ( ^ ), and it acts like,
> well, a permutation. :)
>
> This is also answered faster if asked on the Spirit mailing list.
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Sigh...thanks, that works beautifully. I figured it was something
simple I used to know and had forgotten.