NAME¶

std::basic_regexconstants - std::basic_regexconstants

Synopsis¶

Defined in header <regex>
static constexpr std::regex_constants::syntax_option_type icase =

std::regex_constants::icase;
static constexpr std::regex_constants::syntax_option_type nosubs =
std::regex_constants::nosubs;
static constexpr std::regex_constants::syntax_option_type optimize =
std::regex_constants::optimize;
static constexpr std::regex_constants::syntax_option_type collate =
std::regex_constants::collate;
static constexpr std::regex_constants::syntax_option_type ECMAScript
=
std::regex_constants::ECMAScript;
static constexpr std::regex_constants::syntax_option_type basic =
std::regex_constants::basic;
static constexpr std::regex_constants::syntax_option_type extended =
std::regex_constants::extended;
static constexpr std::regex_constants::syntax_option_type awk =
std::regex_constants::awk;
static constexpr std::regex_constants::syntax_option_type grep =
std::regex_constants::grep;
static constexpr std::regex_constants::syntax_option_type egrep =

std::regex_constants::egrep;
static constexpr std::regex_constants::syntax_option_type multiline = (since C++17)
std::regex_constants::multiline;

std::basic_regex defines several constants that govern general regex matching
syntax.

These constants are duplicated from std::regex_constants:

Grammar option Effect(s)
ECMAScript Use the Modified ECMAScript regular expression grammar.
basic Use the basic POSIX regular expression grammar (grammar
documentation).
extended Use the extended POSIX regular expression grammar (grammar
documentation).
awk Use the regular expression grammar used by the awk utility in
POSIX (grammar documentation).
Use the regular expression grammar used by the grep utility in
grep POSIX. This is effectively the same as the basic option with the
addition of newline '\n' as an alternation separator.
Use the regular expression grammar used by the grep utility, with
egrep the -E option, in POSIX. This is effectively the same as the
extended option with the addition of newline '\n' as an
alternation separator in addition to '|'.
Grammar variation Effect(s)
icase Character matching should be performed without regard to case.
When performing matches, all marked sub-expressions (expr) are
nosubs treated as non-marking sub-expressions (?:expr). No matches are
stored in the supplied std::regex_match structure and mark_count()
is zero.
Instructs the regular expression engine to make matching faster,
optimize with the potential cost of making construction slower. For
example, this might mean converting a non-deterministic FSA to a
deterministic FSA.
collate Character ranges of the form "[a-b]" will be locale sensitive.
multiline (C++17) Specifies that ^ shall match the beginning of a line and $ shall
match the end of a line, if the ECMAScript engine is selected.

At most one grammar option can be chosen out of ECMAScript, basic, extended, awk,
grep, egrep. If no grammar is chosen, ECMAScript is assumed to be selected. The
other options serve as variations, such that std::regex("meow", std::regex::icase)
is equivalent to std::regex("meow", std::regex::ECMAScript|std::regex::icase).

See also¶

syntax_option_type general options controlling regex behavior
(C++11) (typedef)