Iterator Based Generator API

Description

The library provides a couple of free functions to make generating a snap. These generator functions have two forms. The first form, generate, concatenates the output generated by the involved components without inserting any output in between. The second generate_delimited intersperses the output generated by the involved components using the given delimiter generator. Both versions can take in attributes by (constant) reference that hold the attribute values to output.

Header

// forwards to <boost/spirit/home/karma/generate.hpp>
#include <boost/spirit/include/karma_generate.hpp>

For variadic attributes:

// forwards to <boost/spirit/home/karma/generate_attr.hpp>
#include <boost/spirit/include/karma_generate_attr.hpp>

The variadic attributes version of the API allows one or more attributes to be passed into the generate functions. The functions taking two or more attributes are usable when the generator 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) generator type from the supplied attribute type:

// forwards to <boost/spirit/home/karma/detail/generate_auto.hpp>
#include <boost/spirit/include/karma_generate_auto.hpp>

Also, see Include Structure.

Namespace

Name
`boost::spirit::karma::generate`
`boost::spirit::karma::generate_delimited`
`boost::spirit::karma::delimit_flag::predelimit`
`boost::spirit::karma::delimit_flag::dont_predelimit`

Synopsis

namespace boost { namespace spirit { namespace karma
{
    template <typename OutputIterator, typename Expr>
    inline bool
    generate(
        OutputIterator& sink
      , Expr const& expr);

    template <typename OutputIterator, typename Expr
      , typename Attr1, typename Attr2, ..., typename AttrN>
    inline bool
    generate(
        OutputIterator& sink
      , Expr const& expr
      , Attr1 const& attr1, Attr2 const& attr2, ..., AttrN const& attrN);

    template <typename OutputIterator, typename Expr, typename Delimiter>
    inline bool
    generate_delimited(
        OutputIterator& sink
      , Expr const& expr
      , Delimiter const& delimiter
      , BOOST_SCOPED_ENUM(delimit_flag) pre_delimit = delimit_flag::dont_predelimit);

    template <typename OutputIterator, typename Expr, typename Delimiter
      , typename Attr1, typename Attr2, ..., typename AttrN>
    inline bool
    generate_delimited(
        OutputIterator& sink
      , Expr const& expr
      , Delimiter const& delimiter
      , Attr1 const& attr1, Attr2 const& attr2, ..., AttrN const& attrN);

    template <typename OutputIterator, typename Expr, typename Delimiter
      , typename Attr1, typename Attr2, ..., typename AttrN>
    inline bool
    generate_delimited(
        OutputIterator& sink
      , Expr const& expr
      , Delimiter const& delimiter
      , BOOST_SCOPED_ENUM(delimit_flag) pre_delimit
      , Attr1 const& attr1, Attr2 const& attr2, ..., AttrN const& attrN);
}}}

	Note
	Starting with Spirit V2.5 (distributed with Boost V1.47) the placeholder `_val` can be used in semantic actions attached to top level generator components. In this case `_val` refers to the supplied attribute as a whole. For API functions taking more than one attribute argument `_val` will refer to a Fusion vector or references to the attributes.

Spirit.Karma generator API functions based on the automatic creation of the matching generator type:

namespace boost { namespace spirit { namespace karma
{
    template <typename OutputIterator, typename Attr, typename Delimiter>
    inline bool
    generate_delimited(
        OutputIterator& sink
      , Attr const& attr
      , Delimiter const& delimiter
      , BOOST_SCOPED_ENUM(delimit_flag) pre_delimit = delimit_flag::dont_predelimit);

    template <typename OutputIterator, typename Attr>
    inline bool
    generate(
        OutputIterator& sink
      , Attr const& attr);
}}}

All functions above return true if none of the involved generator components failed, and false otherwise. If during the process of the output generation the underlying output stream reports an error, the return value will be false as well.

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 (constant) references to all passed attributes into a `fusion::vector` and forward this as a combined attribute to the corresponding function taking one attribute.

The generate_delimited functions not taking an explicit delimit_flag as one of their arguments don't invoke the passed delimiter before starting to generate output from the generator expression. This can be enabled by using the other version of that function while passing delimit_flag::predelimit to the corresponding argument.

Template parameters

Parameter	Description
`OutputIterator`	`OutputIterator` receiving the generated output.
`Expr`	An expression that can be converted to a Karma generator.
`Delimiter`	Generator used to delimit the output of the expression components.
`Attr`	An attribute type utilized to create the corresponding generator type from.
`Attr1`, `Attr2`, ..., `AttrN`	One or more attributes.