Kleene (*a)

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##### Kleene (`*a`)

###### Description

The kleene operator, `*a`, is a unary operator that matches its operand zero or more times.

###### Header

    // forwards to <boost/spirit/home/qi/operator/kleene.hpp>
    #include <boost/spirit/include/qi_kleene.hpp>

Also, see Include Structure.

###### Model of

> `UnaryParser`

Notation

`a`

  A `Parser`

###### Expression Semantics

Semantics of an expression is defined only where it differs from, or is not defined in `UnaryParser`.

Expression | Semantics
--- | ---
`*a` | Match `a` zero or more times.

###### Attributes

See Compound Attribute Notation.

Expression | Attribute
--- | ---

`*a`

    a: A --> *a: vector<A>
    a: Unused --> *a: Unused

###### Complexity

> The overall complexity of the Kleene star is defined by the complexity of its subject, `a`, multiplied by the number of repetitions. The complexity of the Kleene star itself is O(N), where N is the number successful repetitions.

###### Example

| Note
The test harness for the example(s) below is presented in the Basics Examples section.

Some using declarations:

    using boost::spirit::qi::int_;

Parse a comma separated list of numbers and put them in a vector:

    std::vector<int> attr;
    test_phrase_parser_attr(
        "111, 222, 333, 444, 555", int_ >> *(',' >> int_), attr);
    std::cout
        << attr[0] << ',' << attr[1] << ',' << attr[2] << ','
        << attr[3] << ',' << attr[4]
        << std::endl;