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std::basic_string::assign(3) C++ Standard Libary std::basic_string::assign(3) NAME std::basic_string::assign - std::basic_string::assign Synopsis basic_string& assign( size_type count, CharT (1) (constexpr since ch ); C++20) basic_string& assign( const basic_string& str (2) (constexpr since ); C++20) basic_string& assign( const basic_string& str, size_type pos, size_type (until C++14) count ); basic_string& assign( const basic_string& str, (since C++14) size_type pos, size_type (constexpr since count = npos); C++20) basic_string& assign( basic_string&& str ) (since C++11) noexcept(/* see below */); (4) (constexpr since C++20) basic_string& assign( const CharT* s, (5) (constexpr since size_type count ); C++20) basic_string& assign( const CharT* s ); (6) (constexpr since C++20) template< class InputIt > (3) (constexpr since basic_string& assign( InputIt first, InputIt (7) C++20) last ); basic_string& assign( (since C++11) std::initializer_list<CharT> ilist ); (8) (constexpr since C++20) template< class StringViewLike > (since C++17) basic_string& assign( const StringViewLike& t (9) (constexpr since ); C++20) template< class StringViewLike > (since C++17) basic_string& assign( const StringViewLike& t, (10) (constexpr since C++20) size_type pos, size_type count = npos); Replaces the contents of the string. 1) Replaces the contents with count copies of character ch. 2) Replaces the contents with a copy of str. Equivalent to *this = str;. In particular, allocator propagation may take place. (since C++11) 3) Replaces the contents with a substring [pos, pos + count) of str. If the requested substring lasts past the end of the string, or if count == npos, the resulting substring is [pos, str.size()). If pos > str.size(), std::out_of_range is thrown. 4) Replaces the contents with those of str using move semantics. Equivalent to *this = std::move(str). In particular, allocator propagation may take place. 5) Replaces the contents with copies of the characters in the range [s, s + count). This range can contain null characters. 6) Replaces the contents with those of null-terminated character string pointed to by s. The length of the string is determined by the first null char- acter using Traits::length(s). 7) Replaces the contents with copies of the characters in the range [first, last). This overload does not participate in overload resolution if InputIt does not satisfy LegacyInputIterator. (since C++11) 8) Replaces the contents with those of the initializer list ilist. 9) Implicitly converts t to a string view sv as if by std::ba- sic_string_view<CharT, Traits> sv = t;, then replaces the contents with those of sv, as if by assign(sv.data(), sv.size()). This overload participates in overload resolution only if std::is_convertible_v<const StringViewLike&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false. 10) Implicitly converts t to a string view sv as if by std::ba- sic_string_view<CharT, Traits> sv = t;, then replaces the contents with the characters from the subview [pos, pos + count) of sv. If the requested subview lasts past the end of sv, or if count == npos, the resulting subview is [pos, sv.size()). If pos > sv.size(), std::out_of_range is thrown. This overload participates in overload resolution only if std::is_convertible_v<const StringViewLike&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false. Parameters count - size of the resulting string pos - index of the first character to take ch - value to initialize characters of the string with first, last - range to copy the characters from str - string to be used as source to initialize the charac- ters with s - pointer to a character string to use as source to ini- tialize the string with ilist - std::initializer_list to initialize the characters of the string with t - object (convertible to std::basic_string_view) to ini- tialize the characters of the string with Type requirements - InputIt must meet the requirements of LegacyInputIterator. Return value *this Complexity 1) Linear in count. 2) Linear in size of str. 3) Linear in count. 4) Constant. If alloc is given and alloc != other.get_allocator(), then linear. 5) Linear in count. 6) Linear in size of s. 7) Linear in distance between first and last. 8) Linear in size of ilist. 9) Linear in size of t. Exceptions 4) noexcept specification: noexcept(std::allocator_traits<Allocator>:: propagate_on_container_move_assignment::value || std::allocator_traits<Allocator>::is_always_equal::value) If the operation would result in size() > max_size(), throws std::length_error. If an exception is thrown for any reason, this function has no ef- fect (strong exception safety guarantee). Example // Run this code #include <iostream> #include <iterator> #include <string> int main() { std::string s; // assign(size_type count, CharT ch) s.assign(4, '='); std::cout << s << '\n'; // "====" std::string const c("Exemplary"); // assign(const basic_string& str) s.assign(c); std::cout << c << " == " << s << '\n'; // "Exemplary == Exemplary" // assign(const basic_string& str, size_type pos, size_type count) s.assign(c, 0, c.length() - 1); std::cout << s << '\n'; // "Exemplar"; // assign(basic_string&& str) s.assign(std::string("C++ by ") + "example"); std::cout << s << '\n'; // "C++ by example" // assign(const CharT* s, size_type count) s.assign("C-style string", 7); std::cout << s << '\n'; // "C-style" // assign(const CharT* s) s.assign("C-style\0string"); std::cout << s << '\n'; // "C-style" char mutable_c_str[] = "C-style string"; // assign(InputIt first, InputIt last) s.assign(std::begin(mutable_c_str), std::end(mutable_c_str) - 1); std::cout << s << '\n'; // "C-style string" // assign(std::initializer_list<CharT> ilist) s.assign({'C', '-', 's', 't', 'y', 'l', 'e'}); std::cout << s << '\n'; // "C-style" } Output: ==== Exemplary == Exemplary Exemplar C++ by example C-style C-style C-style string C-style Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior LWG 847 C++98 there was no exception safety added strong exception guarantee safety guar- antee non-normative note stated that swap LWG 2063 C++11 is corrected to require move a valid implementation of assignment move-assign LWG 2579 C++11 assign(const basic_string&) made to propagate allocators did not propagate allocators if needed LWG 2946 C++17 overload (9) caused ambiguity in avoided by making it a some cases template See also assign_range assign a range of characters to a string (C++23) (public member function) constructor constructs a basic_string (public member function) operator= assigns values to the string (public member function) Category: * conditionally noexcept http://cppreference.com 2024.06.10 std::basic_string::assign(3)
NAME | Synopsis | Parameters | Type requirements | Return value | Complexity | Exceptions | Example | Output: | C-style | C-style | C-style | See also | Category:
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