operator==,!=,<,<=,>,>=,<=>(std::basic_string)

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External libraries

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Strings library

Classes
basic_string
basic_string_view (C++17)
char_traits

[edit]

std::basic_string

Member functions
basic_string::basic_string
basic_string::~basic_string
basic_string::operator=
basic_string::assign
basic_string::assign_range (C++23)
basic_string::get_allocator
Element access
basic_string::at
basic_string::operator[]
basic_string::front (DR*)
basic_string::back (DR*)
basic_string::data
basic_string::c_str
basic_string::operator basic_string_view (C++17)
Iterators
basic_string::beginbasic_string::cbegin (C++11)
basic_string::endbasic_string::cend (C++11)
basic_string::rbeginbasic_string::crbegin (C++11)
basic_string::rendbasic_string::crend (C++11)
Search
basic_string::find
basic_string::rfind
basic_string::find_first_of
basic_string::find_first_not_of
basic_string::find_last_of
basic_string::find_last_not_of

Modifiers
basic_string::clear
basic_string::insert
basic_string::insert_range (C++23)
basic_string::erase
basic_string::push_back
basic_string::pop_back (DR*)
basic_string::append
basic_string::append_range (C++23)
basic_string::operator+=
basic_string::replace
basic_string::replace_with_range (C++23)
basic_string::copy
basic_string::resize
basic_string::resize_and_overwrite (C++23)
basic_string::swap
Capacity
basic_string::empty
basic_string::sizebasic_string::length
basic_string::max_size
basic_string::reserve
basic_string::capacity
basic_string::shrink_to_fit (DR*)
Operations
basic_string::compare
basic_string::starts_with (C++20)
basic_string::ends_with (C++20)
basic_string::contains (C++23)
basic_string::substr

swap(std::basic_string)

erase(std::basic_string)erase_if(std::basic_string)

(C++20)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=>

(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Numeric conversions

stoistolstoll (C++11)(C++11)(C++11)
stoulstoull (C++11)(C++11)

stofstodstold (C++11)(C++11)(C++11)
to_string (C++11)
to_wstring (C++11)

Literals

operator""s

(C++14)

Helper classes

hash<std::basic_string>

(C++11)

Deduction guides(C++17)

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Defined in header`<string>`
Compare two`basic_string` objects
template<class CharT,class Traits,class Alloc> bool operator==(conststd::basic_string<CharT,Traits,Alloc>& lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(1)	(noexcept since C++11) (constexpr since C++20)
template<class CharT,class Traits,class Alloc> bool operator!=(conststd::basic_string<CharT,Traits,Alloc>& lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(2)	(until C++20) (noexcept since C++11)
template<class CharT,class Traits,class Alloc> bool operator<(conststd::basic_string<CharT,Traits,Alloc>& lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(3)	(until C++20) (noexcept since C++11)
template<class CharT,class Traits,class Alloc> bool operator<=(conststd::basic_string<CharT,Traits,Alloc>& lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(4)	(until C++20) (noexcept since C++11)
template<class CharT,class Traits,class Alloc> bool operator>(conststd::basic_string<CharT,Traits,Alloc>& lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(5)	(until C++20) (noexcept since C++11)
template<class CharT,class Traits,class Alloc> bool operator>=(conststd::basic_string<CharT,Traits,Alloc>& lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(6)	(until C++20) (noexcept since C++11)
template<class CharT,class Traits,class Alloc> constexpr/comp-cat/ operator<=>(conststd::basic_string<CharT,Traits,Alloc>& lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs)noexcept;	(7)	(since C++20)
Compare a`basic_string` object and null-terminated array of`T`
template<class CharT,class Traits,class Alloc> bool operator==(conststd::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs);	(8)	(constexpr since C++20)
template<class CharT,class Traits,class Alloc> bool operator==(const CharT* lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(9)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator!=(conststd::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs);	(10)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator!=(const CharT* lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(11)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator<(conststd::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs);	(12)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator<(const CharT* lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(13)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator<=(conststd::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs);	(14)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator<=(const CharT* lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(15)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator>(conststd::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs);	(16)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator>(const CharT* lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(17)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator>=(conststd::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs);	(18)	(until C++20)
template<class CharT,class Traits,class Alloc> bool operator>=(const CharT* lhs, conststd::basic_string<CharT,Traits,Alloc>& rhs);	(19)	(until C++20)
template<class CharT,class Traits,class Alloc> constexpr/comp-cat/ operator<=>(conststd::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs);	(20)	(since C++20)

Compares the contents of a string with another string or a null-terminated array ofCharT.

All comparisons are done via thecompare() member function (which itself is defined in terms ofTraits::compare()):

Two strings are equal if both the size oflhs andrhs are equal and each character inlhs has equivalent character inrhs at the same position.

The ordering comparisons are done lexicographically – the comparison is performed by a function equivalent tostd::lexicographical_compareorstd::lexicographical_compare_three_way(since C++20).

1-7) Compares twobasic_string objects.

8-20) Compares abasic_string object and a null-terminated array ofCharT.

The return type of three-way comparison operators (/*comp-cat*/) isTraits::comparison_category if that qualified-id exists and denotes a type,std::weak_ordering otherwise. If/*comp-cat*/ is not a comparison category type, the program is ill-formed.

The<,<=,>,>=, and!= operators aresynthesized fromoperator<=> andoperator== respectively.

(since C++20)

[edit]Parameters

lhs, rhs

strings whose contents to compare

[edit]Return value

1-6,8-19)true if the corresponding comparison holds,false otherwise.

7,20)static_cast</*comp-cat*/>(lhs.compare(rhs)<=>0).

[edit]Complexity

Linear in the size of the strings.

[edit]Notes

If at least one parameter is of typestd::string,std::wstring,std::u8string,std::u16string, orstd::u32string, the return type ofoperator<=> isstd::strong_ordering.

(since C++20)

[edit]Example

This section is incomplete
Reason: no example

[edit]Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
LWG 2064	C++11	whether overloads taking two`basic_string`s are noexcept was inconsistent; overloads taking a`CharT*` were noexcept but might raise UB	made consistent; noexcept removed
LWG 3432	C++20	the return type of`operator<=>` was not required to be a comparison category type	required