Parser Directive Re-Establishing Skipping (skip[])

Parser Directive Re-Establishing Skipping (`skip[]`)

Description

The skip directive is the inverse of lexeme or [qi_no_skip no_skip[]]. While the lexeme directive turns off white space skipping, the skip directive turns it on again. This is simply done by wrapping the parts inside the skip directive:

skip[a]

It is also possible to supply a skip parser to the skip directive:

skip(p)[a] // Use `p` as a skipper for parsing `a`

This makes it possible to:

Perform localized phrase level parsing while doing character level parsing.
Replace the current skipper anywhere with an entirely different skipper while doing phrase level parsing.

Header

// forwards to <boost/spirit/home/qi/directive/skip.hpp>
#include <boost/spirit/include/qi_skip.hpp>

Also, see Include Structure.

Namespace

Name
`boost::spirit::skip // alias: boost::spirit::qi::skip`

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
`skip[a]`	Re-establish the skipper that got inhibited by lexeme or no_skip
`skip(p)[a]`	Use `p` as a skipper for parsing `a`

Attributes

See Compound Attribute Notation.

Expression	Attribute
`skip[a]`	a: A --> skip[a]: A a: Unused --> skip[a]: Unused
`skip(p)[a]`	a: A --> skip(p)[a]: A a: Unused --> skip(p)[a]: Unused

Expression

Attribute

skip[a]

a: A --> skip[a]: A
a: Unused --> skip[a]: Unused

skip(p)[a]

a: A --> skip(p)[a]: A
a: Unused --> skip(p)[a]: Unused

Complexity

The complexity is defined by the complexity of the subject parser, a

Example

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

Some using declarations:

using boost::spirit::qi::skip;
using boost::spirit::qi::int_;
using boost::spirit::ascii::space;

Simple usage of skip[]:

Explicitly specify a skip parser. This parser parses comma delimited numbers, ignoring spaces.

test_parser("1, 2, 3, 4, 5", skip(space)[int_ >> *(',' >> int_)]);