function template

std::swap (basic_string)

template <class charT, class traits, class Alloc>  void swap (basic_string<charT,traits,Alloc>& x,             basic_string<charT,traits,Alloc>& y);

Exchanges the values of two strings

Exchanges the values of basic_string objects x and y, such that after the call to this function, the value of x is the one which was on y before the call, and the value of y is that of x.

This is an overload of the generic algorithm swap that improves its performance by mutually transferring ownership over their internal data to the other object (i.e., the strings exchange references to their data, without actually copying the characters): It behaves as if

x.swap(y) was called.

Parameters

x,y: basic_string objects of the same type (i.e., having both the same template parameters, charT, traits and Alloc).

Return value

none

Example

// swap strings
#include <iostream>
#include <string>

main ()
{
  std::string buyer ("money");
  std::string seller ("goods");

  std::cout << "Before the swap, buyer has " << buyer;
  std::cout << " and seller has " << seller << '\n';

  swap (buyer,seller);

  std::cout << " After the swap, buyer has " << buyer;
  std::cout << " and seller has " << seller << '\n';

  return 0;
}

Output:

Before the swap, buyer has money and seller has goods
 After the swap, buyer has goods and seller has money

Complexity

Constant.

Iterator validity

Any iterators, pointers and references related to both x and y may be invalidated.

Data races

Both objects, x and y, are modified.

Exception safety

If the allocators in both strings compare equal, or if their allocator traits indicate that the allocators shall propagate, the function never throws exceptions (no-throw guarantee).
Otherwise, it causes undefined behavior.