...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
The seek[]
parser-directive skips all input until the subject parser matches. On failure,
the current position is the end of the input.
// forwards to <boost/spirit/repository/home/qi/directive/seek.hpp> #include <boost/spirit/repository/include/qi_seek.hpp>
Also, see Include Structure.
Name |
---|
|
Notation
a
A Parser
.
Semantics of an expression is defined only where it differs from, or is
not defined in UnaryParser
.
Expression |
Semantics |
---|---|
|
Advances until the parser |
See Compound Attribute Notation.
Expression |
Attribute |
---|---|
|
a: A --> seek[a]: A a: Unused --> seek[a]: Unused
|
The overall complexity is defined by the complexity of its subject parser. The complexity of
seek
itself is O(N), where N is the number of unsuccessful matches.
Note | |
---|---|
seeking sequence with skipping
Using seek[lexeme[skip[a >> b]]] does the trick. |
The following example shows a simple use case of the seek[]
directive, parsing C-style comment. (For
the full source of the example, see seek.cpp)
Some namespace aliases:
namespace qi = boost::spirit::qi; namespace repo = boost::spirit::repository;
The input string and its iterators:
std::string str("/*C-style comment*/"); iterator it = str.begin(); iterator end = str.end();
Parsing and showing the result:
if (qi::parse(it, end, "/*" >> repo::qi::seek["*/"])) { std::cout << "-------------------------------- \n"; std::cout << "Parsing succeeded.\n"; std::cout << "---------------------------------\n"; } else { std::cout << "-------------------------------- \n"; std::cout << "Unterminated /* comment.\n"; std::cout << "-------------------------------- \n"; }