The class templatebasic_string stores and manipulates sequences ofcharacter-like objects, which are non-array objects ofTrivialType andStandardLayoutType. The class is dependent neither on the character type nor on the nature of operations on that type. The definitions of the operations are supplied via theTraits template parameter - a specialization ofstd::char_traits or a compatible traits class.

The elements of abasic_string are stored contiguously, that is, for abasic_strings,&*(s.begin()+ n)==&*s.begin()+ n for anyn in[​0​, s.size()), and*(s.begin()+ s.size()) has valueCharT() (a null terminator)(since C++11); or, equivalently, a pointer tos[0] can be passed to functions that expect a pointer to the first element ofan array(until C++11)a null-terminated array(since C++11) ofCharT.

std::basic_string satisfies the requirements ofAllocatorAwareContainer (except that customizedconstruct/destroy are not used for construction/destruction of elements),SequenceContainer andContiguousContainer(since C++17).

If any ofTraits::char_type andAllocator::value_type is different fromCharT, the program is ill-formed.

Several typedefs for common character types are provided:

[edit]Template parameters

[edit]Nested types

[edit]Data members

[edit]Member functions

[edit]Non-member functions

[edit]Literals

[edit]Helper classes

[edit]Deduction guides(since C++17)

[edit]Iterator invalidation

References, pointers, and iterators referring to the elements of abasic_string may be invalidated by any standard library function taking a reference to non-constbasic_string as an argument, such asstd::getline,std::swap, oroperator>>, and by calling non-const member functions, exceptoperator[],at,data,front,back,begin,rbegin,end, andrend.

[edit]Notes

Although it is required that customizedconstruct ordestroy is used when constructing or destroying elements ofstd::basic_string until C++23, all implementations only used the default mechanism. The requirement is corrected byP1072R10 to match existing practice.

[edit]Example

#include <iostream>#include <string> int main(){usingnamespace std::literals; // Creating a string from const char*    std::string str1="hello"; // Creating a string using string literalauto str2="world"s; // Concatenating strings    std::string str3= str1+" "+ str2; // Print out the resultstd::cout<< str3<<'\n';     std::string::size_type pos= str3.find(" ");    str1= str3.substr(pos+1);// the part after the space    str2= str3.substr(0, pos);// the part till the space std::cout<< str1<<' '<< str2<<'\n'; // Accessing an element using subscript operator[]std::cout<< str1[0]<<'\n';    str1[0]='W';std::cout<< str1<<'\n';}

hello worldworld hellowWorld

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

1. ↑TheTraits::char_type case is fixed inP1148R0.

[edit]See also

[edit]External links

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