31 Regular expressions library [re]

The type char_­class_­type is used to represent a character classification and is capable of holding an implementation specific set returned by lookup_­classname.

Returns: char_­traits<charT>​::​length(p).

Returns: c.

Returns: use_­facet<ctype<charT>>(getloc()).tolower(c).

Effects: As if by:

string_type str(first, last);
return use_facet<collate<charT>>(
  getloc()).transform(&*str.begin(), &*str.begin() + str.length());

Effects: If

typeid(use_facet<collate<charT>>) == typeid(collate_byname<charT>)

and the form of the sort key returned by collate_­byname<charT>​::​transform(first, last) is known and can be converted into a primary sort key then returns that key, otherwise returns an empty string.

Returns: a sequence of one or more characters that represents the collating element consisting of the character sequence designated by the iterator range [first, last). Returns an empty string if the character sequence is not a valid collating element.

Returns: an unspecified value that represents the character classification named by the character sequence designated by the iterator range [first, last). If the parameter icase is true then the returned mask identifies the character classification without regard to the case of the characters being matched, otherwise it does honor the case of the characters being matched.329 The value returned shall be independent of the case of the characters in the character sequence. If the name is not recognized then returns char_­class_­type().

Remarks: For regex_­traits<char>, at least the narrow character names in Table 133 shall be recognized. For regex_­traits<wchar_­t>, at least the wide character names in Table 133 shall be recognized.

Effects: Determines if the character c is a member of the character classification represented by f.

Returns: Given the following function declaration:

// for exposition only
template<class C>
  ctype_base::mask convert(typename regex_traits<C>::char_class_type f);

that returns a value in which each ctype_­base​::​mask value corresponding to a value in f named in Table 133 is set, then the result is determined as if by:

ctype_base::mask m = convert<charT>(f);
const ctype<charT>& ct = use_facet<ctype<charT>>(getloc());
if (ct.is(m, c)) {
  return true;
} else if (c == ct.widen('_')) {
  charT w[1] = { ct.widen('w') };
  char_class_type x = lookup_classname(w, w+1);
  return (f&x) == x;
} else {
  return false;
}

[ Example:

regex_traits<char> t;
string d("d");
string u("upper");
regex_traits<char>::char_class_type f;
f = t.lookup_classname(d.begin(), d.end());
f |= t.lookup_classname(u.begin(), u.end());
ctype_base::mask m = convert<char>(f); // m == ctype_­base​::​digit|ctype_­base​::​upper

 — end example ] [ Example:

regex_traits<char> t;
string w("w");
regex_traits<char>::char_class_type f;
f = t.lookup_classname(w.begin(), w.end());
t.isctype('A', f); // returns true
t.isctype('_', f); // returns true
t.isctype(' ', f); // returns false

 — end example ]

Requires: The value of radix shall be 8, 10, or 16.

Returns: the value represented by the digit ch in base radix if the character ch is a valid digit in base radix; otherwise returns -1.

Effects: Imbues this with a copy of the locale loc. [ Note: Calling imbue with a different locale than the one currently in use invalidates all cached data held by *this.  — end note ]

Returns: if no locale has been previously imbued then a copy of the global locale in effect at the time of construction of *this, otherwise a copy of the last argument passed to imbue.

Postconditions: getloc() == loc.

Returns: if no locale has been imbued then a copy of the global locale in effect at the time of construction of *this, otherwise a copy of the last argument passed to imbue.