Книга: Standard Template Library Programmer

basic_string

basic_string<charT, traits, Alloc>

Category: containers

Component type: type

Description

The basic_string class represents a Sequence of characters. It contains all the usual operations of a Sequence, and, additionally, it contains standard string operations such as search and concatenation.

The basic_string class is parameterized by character type, and by that type's Character Traits. Most of the time, however, there is no need to use the basic_string template directly. The types string and wstring are typedefs for, respectively, basic_string<char> and basic_string<wchar_t>.

Some of basic_string's member functions use an unusual method of specifying positions and ranges. In addition to the conventional method using iterators, many of basic_string's member functions use a single value pos of type size_type to represent a position (in which case the position is begin() + pos, and many of basic_string's member functions use two values, pos and n, to represent a range. In that case pos is the beginning of the range and n is its size. That is, the range is [begin() + pos, begin() + pos + n).

Note that the C++ standard does not specify the complexity of basic_string operations. In this implementation, basic_string has performance characteristics very similar to those of vector: access to a single character is O(1), while copy and concatenation are O(N). By contrast, rope has very different performance characteristics: most rope operations have logarithmic complexity.

Note also that, according to the C++ standard, basic_string has very unusual iterator invalidation semantics. Iterators may be invalidated by swap, reserve, insert , and erase (and by functions that are equivalent to insert and/or erase , such as clear, resize, append , and replace). Additionally, however, the first call to any non-const member function, including the non-const version of begin() or operator[], may invalidate iterators. (The intent of these iterator invalidation rules is to give implementors greater freedom in implementation techniques.) In this implementation, begin(), end(), rbegin(), rend(), operator[], c_str(), and data() do not invalidate iterators. In this implementation, iterators are only invalidated by member functions that explicitly change the string's contents.

Example

int main() {
 string s(10u, ' '); // Create a string of ten blanks.
 const char* A = "this is a test";
 s += A;
 cout << "s = " << (s + 'n');
 cout << "As a null-terminated sequence: " << s.c_str() << endl;
 cout << "The sixteenth character is " << s[15] << endl;
 reverse(s.begin(), s.end());
 s.push_back('n');
 cout << s;
}

Definition

Defined in the standard header string.

Template parameters

Parameter Description Default
charT The string's value type: the type of character it contains.
traits The Character Traits type, which encapsulates basic character operations. char_traits<charT>
Alloc The string's allocator, used for internal memory management. alloc

Model of

Random Access Container, Sequence.

Type requirements

In addition to the type requirements imposed by Random Access Container and Sequence:

• charT is a POD ("plain ol' data") type.

• traits is a Character Traits type whose value type is charT

Public base classes

None.

Members

Member Where defined Description
value_type Container The type of object, CharT, stored in the string.
pointer Container Pointer to CharT.
reference Container Reference to CharT
const_reference Container Const reference to CharT
size_type Container An unsigned integral type.
difference_type Container A signed integral type.
static const size_type npos basic_string The largest possible value of type size_type. That is, size_type(-1).
iterator Container Iterator used to iterate through a string. A basic_string supplies Random Access Iterators.
const_iterator Container Const iterator used to iterate through a string.
reverse_iterator Reversible Container Iterator used to iterate backwards through a string.
const_reverse_iterator Reversible Container Const iterator used to iterate backwards through a string.
iterator begin() Container Returns an iterator pointing to the beginning of the string.
iterator end() Container Returns an iterator pointing to the end of the string.
const_iterator begin() const Container Returns a const_iterator pointing to the beginning of the string.
const_iterator end() const Container Returns a const_iterator pointing to the end of the string.
reverse_iterator rbegin() Reversible Container Returns a reverse_iterator pointing to the beginning of the reversed string.
reverse_iterator rend() Reversible Container Returns a reverse_iterator pointing to the end of the reversed string.
const_reverse_iterator rbegin() const Reversible Container Returns a const_reverse_iterator pointing to the beginning of the reversed string.
const_reverse_iterator rend() const Reversible Container Returns a const_reverse_iterator pointing to the end of the reversed string.
size_type size() const Container Returns the size of the string.
size_type length() const basic_string Synonym for size().
size_type max_size() const Container Returns the largest possible size of the string.
size_type capacity() const basic_string See below.
bool empty() const Container true if the string's size is 0.
reference operator[](size_type n) Random Access Container Returns the n'th character.
const_reference operator[](size_type n) const Random Access Container Returns the n'th character.
const charT* c_str() const basic_string Returns a pointer to a null-terminated array of characters representing the string's contents.
const charT* data() const basic_string Returns a pointer to an array of characters (not necessarily null-terminated) representing the string's contents.
basic_string() Container Creates an empty string.
basic_string(const basic_string& s, size_type pos = 0, size_type n = npos) Container, basic_string Generalization of the copy constructor.
basic_string(const charT*) basic_string Construct a string from a null-terminated character array.
basic_string(const charT* s, size_type n) basic_string Construct a string from a character array and a length.
basic_string(size_type n, charT c) Sequence Create a string with n copies of c.
template <class InputIterator> basic_string(InputIterator first, InputIterator last) Sequence Create a string from a range.
~basic_string() Container The destructor.
basic_string& operator=(const basic_string&) Container The assignment operator
basic_string& operator=(const charT* s) basic_string Assign a null-terminated character array to a string.
basic_string& operator=(charT c) basic_string Assign a single character to a string.
void reserve(size_t) basic_string See below.
void swap(basic_string&) Container Swaps the contents of two strings.
iterator insert(iterator pos, const T& x) Sequence Inserts x before pos.
template <class InputIterator > void insert(iterator pos, InputIterator f, InputIterator l) [1] Sequence Inserts the range [first, last) before pos.
void insert(iterator pos, size_type n, const T& x) Sequence Inserts n copies of x before pos.
basic_string& insert(size_type pos, const basic_string& s) basic_string Inserts s before pos.
basic_string& insert(size_type pos, const basic_string& s, size_type pos1, size_type n) basic_string Inserts a substring of s before pos.
basic_string& insert(size_type pos, const charT* s) basic_string Inserts s before pos.
basic_string& insert(size_type pos, const charT* s, size_type n) basic_string Inserts the first n characters of s before pos.
basic_string& insert(size_type pos, size_type n, charT c) basic_string Inserts n copies of c before pos.
basic_string& append(const basic_string& s) basic_string Append s to *this.
basic_string& append(const basic_string& s, size_type pos, size_type n) basic_string Append a substring of s to *this.
basic_string& append(const charT* s) basic_string Append s to *this.
basic_string& append(const charT* s, size_type n) basic_string Append the first n characters of s to *this.
basic_string& append(size_type n, charT c) basic_string Append n copies of c to *this.
template <class InputIterator> basic_string& append(InputIterator first, InputIterator last) basic_string Append a range to *this.
void push_back(charT c) basic_string Append a single character to *this.
basic_string& operator+=(const basic_string& s) basic_string Equivalent to append(s).
basic_string& operator+=(const charT* s) basic_string Equivalent to append(s)
basic_string& operator+=(charT c) basic_string Equivalent to push_back(c)
iterator erase(iterator p) Sequence Erases the character at position p
iterator erase(iterator first, iterator last) Sequence Erases the range [first, last)
basic_string& erase(size_type pos = 0, size_type n = npos) basic_string Erases a range.
void clear() Sequence Erases the entire container.
void resize(size_type n, charT c = charT()) Sequence Appends characters, or erases characters from the end, as necessary to make the string's length exactly n characters.
basic_string& assign(const basic_string&) basic_string Synonym for operator=
basic_string& assign(const basic_string& s, size_type pos, size_type n) basic_string Assigns a substring of s to *this
basic_string& assign(const charT* s, size_type n) basic_string Assigns the first n characters of s to *this.
basic_string& assign(const charT* s) basic_string Assigns a null-terminated array of characters to *this.
basic_string& assign(size_type n, charT c) Sequence Erases the existing characters and replaces them by n copies of c.
template <class InputIterator> basic_string& assign(InputIterator first, InputIterator last) Sequence Erases the existing characters and replaces them by [first, last)
basic_string& replace(size_type pos, size_type n, const basic_string& s) basic_string Replaces a substring of *this with the string s.
basic_string& replace(size_type pos, size_type n, const basic_string& s, size_type pos1, size_type n1) basic_string Replaces a substring of *this with a substring of s.
basic_string& replace(size_type pos, size_type n, const charT* s, size_type n1) basic_string Replaces a substring of *this with the first n1 characters of s.
basic_string& replace(size_type pos, size_type n, const charT* s) basic_string Replaces a substring of *this with a null-terminated character array.
basic_string& replace(size_type pos, size_type n, size_type n1, charT c) basic_string Replaces a substring of *this with n1 copies of c.
basic_string& replace(iterator first, iterator last, const basic_string& s) basic_string Replaces a substring of *this with the string s.
basic_string& replace(iterator first, iterator last, const charT* s, size_type n) basic_string Replaces a substring of *this with the first n characters of s.
basic_string& replace(iterator first, iterator last, const charT* s) basic_string Replaces a substring of *this with a null-terminated character array.
basic_string& replace(iterator first, iterator last, size_type n, charT c) basic_string Replaces a substring of *this with n copies of c.
template <class InputIterator> basic_string& replace(iterator first, iterator last, InputIterator f, InputIterator l) basic_string Replaces a substring of *this with the range [f, l)
size_type copy(charT* buf, size_type n, size_type pos = 0) const basic_string Copies a substring of *this to a buffer.
size_type find(const basic_string& s, size_type pos = 0) const basic_string Searches for s as a substring of *this, beginning at character pos of *this.
size_type find(const charT* s, size_type pos, size_type n) const basic_string Searches for the first n characters of s as a substring of *this, beginning at character pos of *this.
size_type find(const charT* s, size_type pos = 0) const basic_string Searches for a null-terminated character array as a substring of *this, beginning at character pos of *this.
size_type find(charT c, size_type pos = 0) const basic_string Searches for the character c, beginning at character position pos.
size_type rfind(const basic_string& s, size_type pos = npos) const basic_string Searches backward for s as a substring of *this, beginning at character position min(pos, size())
size_type rfind(const charT* s, size_type pos, size_type n) const basic_string Searches backward for the first n characters of s as a substring of *this, beginning at character position min(pos, size())
size_type rfind(const charT* s, size_type pos = npos) const basic_string Searches backward for a null-terminated character array as a substring of *this, beginning at character min(pos, size())
size_type rfind(charT c, size_type pos = npos) const basic_string Searches backward for the character c, beginning at character position min(pos, size().
size_type find_first_of(const basic_string& s, size_type pos = 0) const basic_string Searches within *this, beginning at pos, for the first character that is equal to any character within s.
size_type find_first_of(const charT* s, size_type pos, size_type n) const basic_string Searches within *this, beginning at pos, for the first character that is equal to any character within the first n characters of s.
size_type find_first_of(const charT* s, size_type pos = 0) const basic_string Searches within *this, beginning at pos, for the first character that is equal to any character within s.
size_type find_first_of(charT c, size_type pos = 0) const basic_string Searches within *this, beginning at pos, for the first character that is equal to c.
size_type find_first_not_of(const basic_string& s, size_type pos = 0) const basic_string Searches within *this, beginning at pos, for the first character that is not equal to any character within s.
size_type find_first_not_of(const charT* s, size_type pos, size_type n) const basic_string Searches within *this, beginning at pos, for the first character that is not equal to any character within the first n characters of s.
size_type find_first_not_of(const charT* s, size_type pos = 0) const basic_string Searches within *this, beginning at pos, for the first character that is not equal to any character within s.
size_type find_first_not_of(charT c, size_type pos = 0) const basic_string Searches within *this, beginning at pos, for the first character that is not equal to c.
size_type find_last_of(const basic_string& s, size_type pos = npos) const basic_string Searches backward within *this, beginning at min(pos, size()), for the first character that is equal to any character within s.
size_type find_last_of(const charT* s, size_type pos, size_type n) const basic_string Searches backward within *this, beginning at min(pos, size()), for the first character that is equal to any character within the first n characters of s.
size_type find_last_of(const charT* s, size_type pos = npos) const basic_string Searches backward *this, beginning at min(pos, size()), for the first character that is equal to any character within s.
size_type find_last_of(charT c, size_type pos = npos) const basic_string Searches backward *this, beginning at min(pos, size()), for the first character that is equal to c.
size_type find_last_not_of(const basic_string& s, size_type pos = npos) const basic_string Searches backward within *this, beginning at min(pos, size()), for the first character that is not equal to any character within s.
size_type find_last_not_of(const charT* s, size_type pos, size_type n) const basic_string Searches backward within *this, beginning at min(pos, size()), for the first character that is not equal to any character within the first n characters of s.
size_type find_last_not_of(const charT* s, size_type pos = npos) const basic_string Searches backward *this, beginning at min(pos, size()), for the first character that is not equal to any character within s.
size_type find_last_not_of(charT c, size_type pos = npos) const basic_string Searches backward *this, beginning at min(pos, size()), for the first character that is not equal to c.
basic_string substr(size_type pos = 0, size_type n = npos) const basic_string Returns a substring of *this.
int compare(const basic_string& s) const basic_string Three-way lexicographical comparison of s and *this.
int compare(size_type pos, size_type n, const basic_string& s) const basic_string Three-way lexicographical comparison of s and a substring of *this.
int compare(size_type pos, size_type n, const basic_string& s, size_type pos1, size_type n1) const basic_string Three-way lexicographical comparison of a substring of s and a substring of *this
int compare(const charT* s) const basic_string Three-way lexicographical comparison of s and *this.
int compare(size_type pos, size_type n, const charT* s, size_type len = npos) const basic_string Three-way lexicographical comparison of the first min(len, traits::length(s)) characters of s and a substring of *this.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const basic_string<charT, traits, Alloc>& s1, const basic_string<charT, traits, Alloc>& s2) basic_string String concatenation. A global function, not a member function.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const charT* s1, const basic_string<charT, traits, Alloc>& s2) basic_string String concatenation. A global function, not a member function.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const basic_string<charT, traits, Alloc>& s1, const charT* s2) basic_string String concatenation. A global function, not a member function.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(charT c, const basic_string<charT, traits, Alloc>& s2) basic_string String concatenation. A global function, not a member function.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const basic_string<charT, traits, Alloc>& s1, charT c) basic_string String concatenation. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator==(const basic_string<charT, traits, Alloc>& s1, const basic_string<charT, traits, Alloc>& s2) Container String equality. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator==(const charT* s1, const basic_string<charT, traits, Alloc>& s2) basic_string String equality. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator==(const basic_string<charT, traits, Alloc>& s1, const charT* s2) basic_string String equality. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator!=(const basic_string<charT, traits, Alloc>& s1, const basic_string<charT, traits, Alloc>& s2) Container String inequality. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator!=(const charT* s1, const basic_string<charT, traits, Alloc>& s2) basic_string String inequality. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator!=(const basic_string<charT, traits, Alloc>& s1, const charT* s2) basic_string String inequality. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator<(const basic_string<charT, traits, Alloc>& s1, const basic_string<charT, traits, Alloc>& s2) Container String comparison. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator<(const charT* s1, const basic_string<charT, traits, Alloc>& s2) basic_string String comparison. A global function, not a member function.
template<class charT, class traits, class Alloc> bool operator<(const basic_string<charT, traits, Alloc>& s1, const charT* s2) basic_string String comparison. A global function, not a member function.
template<class charT, class traits, class Alloc> void swap(basic_string<charT, traits, Alloc>& s1, basic_string<charT, traits, Alloc>& s2) Container Swaps the contents of two strings.
template<class charT, class traits, class Alloc> basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& is, basic_string<charT, traits, Alloc>& s) basic_string Reads s from the input stream is
template<class charT, class traits, class Alloc> basic_ostream<charT, traits>& operator<<(basic_istream<charT, traits>& os, const basic_string<charT, traits, Alloc>& s) basic_string Writes s to the output stream os
template<class charT, class traits, class Alloc> basic_istream<charT, traits>& getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Alloc>& s, charT delim) basic_string Reads a string from the input stream is, stopping when it reaches delim
template<class charT, class traits, class Alloc> basic_istream<charT, traits>& getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Alloc>& s) basic_string Reads a single line from the input stream is

New members

These members are not defined in the Random Access Container and Sequence: requirements, but are specific to basic_string.

Member Description
static const size_type npos The largest possible value of type size_type. That is, size_type(-1).
size_type length() const Equivalent to size().
size_type capacity() const Number of elements for which memory has been allocated. That is, the size to which the string can grow before memory must be reallocated. capacity() is always greater than or equal to size().
const charT* c_str() const Returns a pointer to a null-terminated array of characters representing the string's contents. For any string s it is guaranteed that the first s.size() characters in the array pointed to by s.c_str() are equal to the character in s, and that s.c_str()[s.size()] is a null character. Note, however, that it not necessarily the first null character. Characters within a string are permitted to be null.
const charT* data() const Returns a pointer to an array of characters, not necessarily null-terminated, representing the string's contents. data() is permitted, but not required, to be identical to c_str(). The first size() characters of that array are guaranteed to be identical to the characters in *this. The return value of data() is never a null pointer, even if size() is zero.
basic_string(const basic_string& s, size_type pos = 0, size_type n = npos) Constructs a string from a substring of s. The substring begins at character position pos and terminates at character position pos + n or at the end of s, whichever comes first. This constructor throws out_of_range if pos > s.size(). Note that when pos and n have their default values, this is just a copy constructor.
basic_string(const charT* s) Equivalent to basic_string(s, s + traits::length(s)).
basic_string(const charT* s, size_type n) Equivalent to basic_string(s, s + n).
basic_string& operator=(const charT* s) Equivalent to operator=(basic_string(s)).
basic_string& operator=(charT c) Assigns to *this a string whose size is 1 and whose contents is the single character c.
void reserve(size_t n) Requests that the string's capacity be changed; the postcondition for this member function is that, after it is called, capacity() >= n. You may request that a string decrease its capacity by calling reserve() with an argument less than the current capacity. (If you call reserve() with an argument less than the string's size, however, the capacity will only be reduced to size(). A string's size can never be greater than its capacity.) reserve() throws length_error if n > max_size().
basic_string& insert(size_type pos, const basic_string& s) If pos > size(), throws out_of_range. Otherwise, equivalent to insert(begin() + pos, s.begin(), s.end()).
basic_string& insert(size_type pos, const basic_string& s, size_type pos1, size_type n) If pos > size() or pos1 > s.size(), throws out_of_range. Otherwise, equivalent to insert(begin() + pos, s.begin() + pos1, s.begin() + pos1 + min(n, s.size() – pos1)).
basic_string& insert(size_type pos, const charT* s) If pos > size(), throws out_of_range. Otherwise, equivalent to insert(begin() + pos, s, s + traits::length(s))
basic_string& insert(size_type pos, const charT* s, size_type n) If pos > size(), throws out_of_range. Otherwise, equivalent to insert(begin() + pos, s, s + n).
basic_string& insert(size_type pos, size_type n, charT c) If pos > size(), throws out_of_range. Otherwise, equivalent to insert(begin() + pos, n, c).
basic_string& append(const basic_string& s) Equivalent to insert(end(), s.begin(), s.end()).
basic_string& append(const basic_string& s, size_type pos, size_type n) If pos > s.size(), throws out_of_range. Otherwise, equivalent to insert(end(), s.begin() + pos, s.begin() + pos + min(n, s.size() – pos)).
basic_string& append(const charT* s) Equivalent to insert(end(), s, s + traits::length(s)).
basic_string& append(const charT* s, size_type n) Equivalent to insert(end(), s, s + n).
basic_string& append(size_type n, charT c) Equivalent to insert(end(), n, c).
template<class InputIterator> basic_string& append(InputIterator first, InputIterator last) Equivalent to insert(end(), first, last).
void push_back(charT c) Equivalent to insert(end(), c)
basic_string& operator+=(const basic_string& s) Equivalent to append(s).
basic_string& operator+=(const charT* s) Equivalent to append(s)
basic_string& operator+=(charT c) Equivalent to push_back(c)
basic_string& erase(size_type pos = 0, size_type n = npos) If pos > size(), throws out_of_range. Otherwise, equivalent to erase(begin() + pos, begin() + pos + min(n, size() – pos)).
basic_string& assign(const basic_string& s) Synonym for operator=
basic_string& assign(const basic_string& s, size_type pos, size_type n) Equivalent to (but probably faster than) clear() followed by insert(0, s, pos, n).
basic_string& assign(const charT* s, size_type n) Equivalent to (but probably faster than) clear() followed by insert(0, s, n).
basic_string& assign(const charT* s) Equivalent to (but probably faster than) clear() followed by insert(0, s).
basic_string& replace(size_type pos, size_type n, const basic_string& s) Equivalent to erase(pos, n) followed by insert(pos, s).
basic_string& replace(size_type pos, size_type n, const basic_string& s, size_type pos1, size_type n1) Equivalent to erase(pos, n) followed by insert(pos, s, pos1, n1).
basic_string& replace(size_type pos, size_type n, const charT* s, size_type n1) Equivalent to erase(pos, n) followed by insert(pos, s, n1).
basic_string& replace(size_type pos, size_type n, const charT* s) Equivalent to erase(pos, n) followed by insert(pos, s).
basic_string& replace(size_type pos, size_type n, size_type n1, charT c) Equivalent to erase(pos, n) followed by insert(pos, n1, c).
basic_string& replace(iterator first, iterator last, const basic_string& s) Equivalent to insert(erase(first, last), s.begin(), s.end()).
basic_string& replace(iterator first, iterator last, const charT* s, size_type n) Equivalent to insert(erase(first, last), s, s + n).
basic_string& replace(iterator first, iterator last, const charT* s) Equivalent to insert(erase(first, last), s, s + traits::length(s)).
basic_string& replace(iterator first, iterator last, size_type n, charT c) Equivalent to insert(erase(first, last), n, c).
template<class InputIterator> basic_string& replace(iterator first, iterator last, InputIterator f, InputIterator l) Equivalent to insert(erase(first, last), f, l).
size_type copy(charT* buf, size_type n, size_type pos = 0) const Copies at most n characters from *this to a character array. Throws out_of_range if pos > size(). Otherwise, equivalent to copy(begin() + pos, begin() + pos + min(n, size()), buf). Note that this member function does nothing other than copy characters from *this to buf; in particular, it does not terminate buf with a null character.
size_type find(const basic_string& s, size_type pos = 0) const Searches for s as a substring of *this, beginning at character position pos. It is almost the same as search, except that search tests elements for equality using operator== or a user-provided function object, while this member function uses traits::eq. Returns the lowest character position N such that pos <= N and pos + s.size() <= size() and such that, for every i less than s.size(), (*this)[N + i] compares equal to s[i]. Returns npos if no such position N exists. Note that it is legal to call this member function with arguments such that s.size() > size() – pos, but such a search will always fail.
size_type find(const charT* s, size_type pos, size_type n) const Searches for the first n characters of s as a substring of *this, beginning at character pos of *this. This is equivalent to find(basic_string(s, n), pos).
size_type find(const charT* s, size_type pos = 0) const Searches for a null-terminated character array as a substring of *this, beginning at character pos of *this. This is equivalent to find(basic_string(s), pos).
size_type find(charT c, size_type pos = 0) const Searches for the character c, beginning at character position pos. That is, returns the first character position N greater than or equal to pos, and less than size(), such that (*this)[N] compares equal to c. Returns npos if no such character position N exists.
size_type rfind(const basic_string& s, size_type pos = npos) const Searches backward for s as a substring of *this. It is almost the same as find_end, except that find_end tests elements for equality using operator== or a user-provided function object, while this member function uses traits::eq. This member function returns the largest character position N such that N <= pos and N + s.size() <= size(), and such that, for every i less than s.size(), (*this)[N + i] compares equal to s[i]. Returns npos if no such position N exists. Note that it is legal to call this member function with arguments such that s.size() > size(), but such a search will always fail.
size_type rfind(const charT* s, size_type pos, size_type n) const Searches backward for the first n characters of s as a substring of *this. Equivalent to rfind(basic_string(s, n), pos).
size_type rfind(const charT* s, size_type pos = npos) const Searches backward for a null-terminated character array as a substring of *this. Equivalent to rfind(basic_string(s), pos).
size_type rfind(charT c, size_type pos = npos) const Searches backward for the character c. That is, returns the largest character position N such that N <= pos and N < size(), and such that (*this)[N] compares equal to c. Returns npos if no such character position exists.
size_type find_first_of(const basic_string& s, size_type pos = 0) const Searches within *this, beginning at pos, for the first character that is equal to any character within s. This is similar to the standard algorithm find_first_of, but differs because find_first_of compares characters using operator== or a user-provided function object, while this member function uses traits::eq. Returns the smallest character position N such that pos <= N < size(), and such that (*this)[N] compares equal to some character within s. Returns npos if no such character position exists.
size_type find_first_of(const charT* s, size_type pos, size_type n) const Searches within *this, beginning at pos, for the first character that is equal to any character within the range [s, s+n). That is, returns the smallest character position N such that pos <= N < size(), and such that (*this)[N] compares equal to some character in [s, s+n). Returns npos if no such character position exists.
size_type find_first_of(const charT* s, size_type pos = 0) const Equivalent to find_first_of(s, pos, traits::length(s)).
size_type find_first_of(charT c, size_type pos = 0) const Equivalent to find(c, pos).
size_type find_first_not_of(const basic_string& s, size_type pos = 0) const Searches within *this, beginning at pos, for the first character that is not equal to any character within s. Returns the smallest character position N such that pos <= N < size(), and such that (*this)[N] does not compare equal to any character within s. Returns npos if no such character position exists.
size_type find_first_not_of(const charT* s, size_type pos, size_type n) const Searches within *this, beginning at pos, for the first character that is not equal to any character within the range [s, s+n). That is, returns the smallest character position N such that pos <= N < size(), and such that (*this)[N] does not compare equal to any character in [s, s+n). Returns npos if no such character position exists.
size_type find_first_not_of(const charT* s, size_type pos = 0) const Equivalent to find_first_not_of(s, pos, traits::length(s)).
size_type find_first_not_of(charT c, size_type pos = 0) const Returns the smallest character position N such that pos <= N < size(), and such that (*this)[N] does not compare equal to c. Returns npos if no such character position exists.
size_type find_last_of(const basic_string& s, size_type pos = npos) const Searches backward within *this for the first character that is equal to any character within s. That is, returns the largest character position N such that N <= pos and N < size(), and such that (*this)[N] compares equal to some character within s. Returns npos if no such character position exists.
size_type find_last_of(const charT* s, size_type pos, size_type n) const Searches backward within *this for the first character that is equal to any character within the range [s, s+n). That is, returns the largest character position N such that N <= pos and N < size(), and such that (*this)[N] compares equal to some character within [s, s+n). Returns npos if no such character position exists.
size_type find_last_of(const charT* s, size_type pos = npos) const Equivalent to find_last_of(s, pos, traits::length(s)).
size_type find_last_of(charT c, size_type pos = npos) const Equivalent to rfind(c, pos).
size_type find_last_not_of(const basic_string& s, size_type pos = npos) const Searches backward within *this for the first character that is not equal to any character within s. That is, returns the largest character position N such that N <= pos and N < size(), and such that (*this)[N] does not compare equal to any character within s. Returns npos if no such character position exists.
size_type find_last_not_of(const charT* s, size_type pos, size_type n) const Searches backward within *this for the first character that is not equal to any character within [s, s+n). That is, returns the largest character position N such that N <= pos and N < size(), and such that (*this)[N] does not compare equal to any character within [s, s+n). Returns npos if no such character position exists.
size_type find_last_not_of(const charT* s, size_type pos = npos) const Equivalent to find_last_of(s, pos, traits::length(s)).
size_type find_last_not_of(charT c, size_type pos = npos) const Searches backward *this for the first character that is not equal to c. That is, returns the largest character position N such that N <= pos and N < size(), and such that (*this)[N] does not compare equal to c.
basic_string substr(size_type pos = 0, size_type n = npos) const Equivalent to basic_string(*this, pos, n).
int compare(const basic_string& s) const Three-way lexicographical comparison of s and *this, much like strcmp. If traits::compare(data, s.data(), min(size(), s.size())) is nonzero, then it returns that nonzero value. Otherwise returns a negative number if size() < s.size(), a positive number if size() > s.size(), and zero if the two are equal.
int compare(size_type pos, size_type n, const basic_string& s) const Three-way lexicographical comparison of s and a substring of *this. Equivalent to basic_string(*this, pos, n).compare(s).
int compare(size_type pos, size_type n, const basic_string& s, size_type pos1, size_type n1) const Three-way lexicographical comparison of a substring of s and a substring of *this. Equivalent to basic_string(*this, pos, n).compare(basic_string(s, pos1, n1)).
int compare(const charT* s) const Three-way lexicographical comparison of s and *this. Equivalent to compare(basic_string(s)).
int compare(size_type pos, size_type n, const charT* s, size_type len = npos) const Three-way lexicographical comparison of the first min(len, traits::length(s) characters of s and a substring of *this. Equivalent to basic_string(*this, pos, n).compare(basic_string(s, min(len, traits::length(s)))).
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const basic_string<charT, traits, Alloc>& s1, const basic_string<charT, traits, Alloc>& s2) String concatenation. Equivalent to creating a temporary copy of s, appending s2, and then returning the temporary copy.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const charT* s1, const basic_string<charT, traits, Alloc>& s2) String concatenation. Equivalent to creating a temporary basic_string object from s1, appending s2, and then returning the temporary object.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const basic_string<charT, traits, Alloc>& s1, const charT* s2) String concatenation. Equivalent to creating a temporary copy of s, appending s2, and then returning the temporary copy.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(charT c, const basic_string<charT, traits, Alloc>& s2) String concatenation. Equivalent to creating a temporary object with the constructor basic_string(1, c), appending s2, and then returning the temporary object.
template<class charT, class traits, class Alloc> basic_string<charT, traits, Alloc> operator+(const basic_string<charT, traits, Alloc>& s1, charT c) String concatenation. Equivalent to creating a temporary object, appending c with push_back, and then returning the temporary object.
template<class charT, class traits, class Alloc> bool operator==(const charT* s1, const basic_string<charT, traits, Alloc>& s2) String equality. Equivalent to basic_string(s1).compare(s2) == 0.
template<class charT, class traits, class Alloc> bool operator==(const basic_string<charT, traits, Alloc>& s1, const charT* s2) String equality. Equivalent to basic_string(s1).compare(s2) == 0.
template<class charT, class traits, class Alloc> bool operator!=(const charT* s1, const basic_string<charT, traits, Alloc>& s2) String inequality. Equivalent to basic_string(s1).compare(s2) == 0.
template<class charT, class traits, class Alloc> bool operator!=(const basic_string<charT, traits, Alloc>& s1, const charT* s2) String inequality. Equivalent to !(s1 == s2).
template<class charT, class traits, class Alloc> bool operator<(const charT* s1, const basic_string<charT, traits, Alloc>& s2) String comparison. Equivalent to !(s1 == s2).
template<class charT, class traits, class Alloc> bool operator<(const basic_string<charT, traits, Alloc>& s1, const charT* s2) String comparison. Equivalent to !(s1 == s2).
template<class charT, class traits, class Alloc> basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& is, basic_string<charT, traits, Alloc>& s) Reads s from the input stream is. Specifically, it skips whitespace, and then replaces the contents of s with characters read from the input stream. It continues reading characters until it encounters a whitespace character (in which case that character is not extracted), or until end-of-file, or, if is.width() is nonzero, until it has read is.width() characters. This member function resets is.width() to zero.
template<class charT, class traits, class Alloc> basic_ostream<charT, traits>& operator>>(basic_istream<charT, traits>& is, const basic_string<charT, traits, Alloc>& s) Writes s to the output stream is. It writes max(s.size(), is.width()) characters, padding as necessary. This member function resets is.width() to zero.
template<class charT, class traits, class Alloc> basic_istream<charT, traits>& getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Alloc>& s, charT delim) Replaces the contents of s with characters read from the input stream. It continues reading characters until it encounters the character delim (in which case that character is extracted but not stored in s ), or until end of file. Note that getline , unlike operator>>, does not skip whitespace. As the name suggests, it is most commonly used to read an entire line of text precisely as the line appears in an input file.
template<class charT, class traits, class Alloc> basic_istream<charT, traits>& getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Alloc>& s) Equivalent to getline(is, s, is.widen('n)).

See also

rope, vector, Character Traits

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