Iterator Based Parser API

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##### Iterator Based Parser API

###### Description

The library provides a couple of free functions to make parsing a snap. These parser functions have two forms. The first form `parse` works on the character level. The second `phrase_parse` works on the phrase level and requires skip parser. Both versions can take in attributes by reference that will hold the parsed values on a successful parse.

###### Header

    // forwards to <boost/spirit/home/qi/parse.hpp>
    #include <boost/spirit/include/qi_parse.hpp>

For variadic attributes:

    // forwards to <boost/spirit/home/qi/parse_attr.hpp>
    #include <boost/spirit/include/qi_parse_attr.hpp>

The variadic attributes version of the API allows one or more attributes to be passed into the parse functions. The functions taking two or more are usable when the parser expression is a Sequence only. In this case each of the attributes passed have to match the corresponding part of the sequence.

For the API functions deducing the correct (matching) parser type from the supplied attribute type:

    // forwards to <boost/spirit/home/qi/detail/parse_auto.hpp>
    #include <boost/spirit/include/qi_parse_auto.hpp>

Also, see Include Structure.

###### Namespace

Name
`boost::spirit::qi::parse`
`boost::spirit::qi::phrase_parse`
`boost::spirit::qi::skip_flag::postskip`
`boost::spirit::qi::skip_flag::dont_postskip`

###### Synopsis

    namespace boost { namespace spirit { namespace qi
    {
        template <typename Iterator, typename Expr>
        inline bool
        parse(
            Iterator& first
          , Iterator last
          , Expr const& expr);

        template <typename Iterator, typename Expr
          , typename Attr1, typename Attr2, ..., typename AttrN>
        inline bool
        parse(
            Iterator& first
          , Iterator last
          , Expr const& expr
          , Attr1& attr1, Attr2& attr2, ..., AttrN& attrN);

        template <typename Iterator, typename Expr, typename Skipper>
        inline bool
        phrase_parse(
            Iterator& first
          , Iterator last
          , Expr const& expr
          , Skipper const& skipper
          , BOOST_SCOPED_ENUM(skip_flag) post_skip = skip_flag::postskip);

        template <typename Iterator, typename Expr, typename Skipper
          , typename Attr1, typename Attr2, ..., typename AttrN>
        inline bool
        phrase_parse(
            Iterator& first
          , Iterator last
          , Expr const& expr
          , Skipper const& skipper
          , Attr1& attr1, Attr2& attr2, ..., AttrN& attrN);

        template <typename Iterator, typename Expr, typename Skipper
          , typename Attr1, typename Attr2, ..., typename AttrN>
        inline bool
        phrase_parse(
            Iterator& first
          , Iterator last
          , Expr const& expr
          , Skipper const& skipper
          , BOOST_SCOPED_ENUM(skip_flag) post_skip
          , Attr1& attr1, Attr2& attr2, ..., AttrN& attrN);
    }}}

Spirit.Qi parser API functions based on the automatic creation of the matching parser type:

    namespace boost { namespace spirit { namespace qi
    {
        template <typename Iterator, typename Attr>
        inline bool
        parse(
            Iterator& first
          , Iterator last
          , Attr& attr);

        template <typename Iterator, typename Attr, typename Skipper>
        inline bool
        phrase_parse(
            Iterator& first
          , Iterator last
          , Attr& attr
          , Skipper const& skipper
          , BOOST_SCOPED_ENUM(skip_flag) post_skip = skip_flag::postskip);
    }}}

All functions above return `true` if none of the involved parser components failed, and `false` otherwise.

The maximum number of supported arguments is limited by the preprocessor constant `SPIRIT_ARGUMENTS_LIMIT`. This constant defaults to the value defined by the preprocessor constant `PHOENIX_LIMIT` (which in turn defaults to `10`).

| Note
The variadic functions with two or more attributes internally combine references to all passed attributes into a `fusion::vector` and forward this as a combined attribute to the corresponding one attribute function.

The `phrase_parse` functions not taking an explicit `skip_flag` as one of their arguments invoke the passed skipper after a successful match of the parser expression. This can be inhbited by using the other versions of that function while passing `skip_flag::dont_postskip` to the corresponding argument.

Parameter | Description
--- | ---
`Iterator` | `ForwardIterator` pointing to the source to parse.
`Expr` | An expression that can be converted to a Qi parser.
`Skipper` | Parser used to skip white spaces.
`Attr` | An attribute type utilized to create the corresponding parser type from.
`Attr1`, `Attr2`, ..., `AttrN` | One or more attributes.