Difference between revisions of "cpp/string/basic string/operator+"

Revision as of 16:39, 31 October 2018

Returns a string containing characters from lhs followed by the characters from rhs.

Parameters

Return value

1) basic_string<CharT,Traits,Alloc>(lhs).append(rhs)

2) basic_string<CharT,Traits,Alloc>(lhs) + rhs

3) basic_string<CharT,Traits,Alloc>(1,lhs) + rhs

4) lhs + basic_string<CharT,Traits,Alloc>(rhs)

5) lhs + basic_string<CharT,Traits,Alloc>(1,rhs)

6) std::move(lhs.append(rhs))

7) std::move(rhs.insert(0, lhs))

8) std::move(lhs.append(rhs)) or std::move(rhs.insert(0, lhs))

9) std::move(rhs.insert(0, lhs))

10) std::move(rhs.insert(0, 1, lhs))

11) std::move(lhs.append(rhs))

12) std::move(lhs.append(1, rhs))

Notes

operator+ should be used with great caution when stateful allocators are involved (such as when std::pmr::string is used). The allocator used for the result can vary from overload to overload, and the standard is occasionally contradictory. For many of the overloads, the allocator propagation behavior varies across major standard library implementations and differs from the behavior depicted in the standard.

For better and portable control over allocators, member functions like append(), insert(), and operator+=() should be used on a result string constructed with the desired allocator.

Example

#include <iostream>
#include <string>
 
int main()
{
    std::string s1 = "Hello";
    std::string s2 = "world";
    std::cout << s1 + ' ' + s2 + "!\n";
}

Hello world!

See also