28 Regular expressions library [re]

28.8 Class template basic_regex [re.regex]

28.8.1 basic_regex constants [re.regex.const]

static constexpr regex_constants::syntax_option_type
  icase = regex_constants::icase;
static constexpr regex_constants::syntax_option_type
  nosubs = regex_constants::nosubs;
static constexpr regex_constants::syntax_option_type
  optimize = regex_constants::optimize;
static constexpr regex_constants::syntax_option_type
  collate = regex_constants::collate;
static constexpr regex_constants::syntax_option_type
  ECMAScript = regex_constants::ECMAScript;
static constexpr regex_constants::syntax_option_type
  basic = regex_constants::basic;
static constexpr regex_constants::syntax_option_type
  extended = regex_constants::extended;
static constexpr regex_constants::syntax_option_type
  awk = regex_constants::awk;
static constexpr regex_constants::syntax_option_type
  grep = regex_constants::grep;
static constexpr regex_constants::syntax_option_type
  egrep = regex_constants::egrep;
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The static constant members are provided as synonyms for the constants declared in namespace regex_constants.