Cpp long int to string

Функция преобразования long long в string

Подскажите как можно преобразовать 16-значное число в string . Или для этого подойдет itoa() ?

Ответы (4 шт):

#include #include int main() < std::stringstream sstream; std::string snum; long long num = 999L; sstream > snum; // или snum = sstream.str() std::cout

Можно написать обобщенную функцию:

#include #include template std::string to_str(const T &obj) < std::stringstream sstream; sstream int main()

Обновление: пример на чистом C.

P.S. Все-таки, если хотите на чистом C, то не стоит писать в заголовке вопроса и в тегах "C++".

Имеется перегруженная стандартная функция с именем std::to_string , которую вы можете использовать для преобразования целочисленных значений (и значений с плавающей точкой) в строку.

Вывод программы на консоль следующий:

Sequence of numbers: -1, 2, -3, 4 

string to_string(int val); string to_string(unsigned val); string to_string(long val); string to_string(unsigned long val); string to_string(long long val); string to_string(unsigned long long val); string to_string(float val); string to_string(double val); string to_string(long double val); 

Имейте в виду, что если вы работаете с MS VC++ 2010, то у вас могут быть проблемы с неоднозначностью вызова функции, так как эта функция в MS VC++ определена не для всех указанных в списке типов.

Узнать, сколько десятичных знаков может храниться в числе вы можете с помощью класса std::numeric_limits . Например, следующая программа

#include #include int main() < std::cout ::digits10 ::digits10

в зависимости от платформы, где запущена программа, может иметь следующий вывод на консоль:

Для С++11 и старше самый простой вариант использовать функцию std::to_string

std::string ulonglongToStr(int64_t l, int base) < char buff[67]; // length of MAX_ULLONG in base 2 buff[66] = 0; char *p = buff + 66; const char _zero = '0'; if (base != 10) < while (l != 0) < int c = l % base; --p; if (c < 10) *p = '0' + c; else *p = c - 10 + 'a'; l /= base; >> else < while (l != 0) < int c = l % base; *(--p) = _zero + c; l /= base; >> return p; > std::string longlongtoStr(int64_t l, int base)

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Convert Long to String in C++ | (3 ways)

In this article, we will learn about three different ways to convert a long to a string in C++ i.e.

1. Using to_string() function
2. Using stingstream
3. Using Boost’s lexical_cast() function.

Let’s discuss them one by one.

Convert long to string using to_string()

C++ provides a function std::to_string() for converting values of different types to string type. We can use this to convert a long to string. For example,

#include #include using namespace std; int main() < long num = 102612; // Convert long to string string num_str = to_string(num); cout

We passed a long to the to_string() function, and it converted the given long to a string and returned the string object. If you pass a negative long to the to_string(), it will convert to a string with a minus symbol.

Frequently Asked:

Convert long to string using stringstream in C++

C++ provides a class stringstream, which provides a stream-like functionality. We can insert different types of elements in stringstream and get a final string object from the stream. Check out this example,

#include #include #include using namespace std; int main() < long num = 1789; stringstream stream; // Add long to the stream stream<Are you a C++ programmer eager to step up your game?

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In the stringstream, we inserted a long, and the stream converted the long to string. Then, in the end, we requested a string object from the stream.

Convert long to string using boost::lexical_cast()

The C++ boost library provides a template function for data type conversion. It helps to convert elements from one data type to another. We can use that to convert a long to a string. For example,

#include #include #include using namespace std; using namespace boost; int main() < long num = 3456; // Convert long to string using boost library string str = lexical_cast(num); cout

We learned about three different ways to convert a long to a string in C++.

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std:: to_string

Let buf be an internal to the conversion functions buffer, sufficiently large to contain the result of conversion.

Contents

[edit] Parameters

[edit] Return value

A string holding the converted value.

[edit] Exceptions

May throw std::bad_alloc from the std::string constructor.

[edit] Notes

• With floating point types std::to_string may yield unexpected results as the number of significant digits in the returned string can be zero, see the example.
• The return value may differ significantly from what std::cout prints by default, see the example.
• std::to_string relies on the current locale for formatting purposes, and therefore concurrent calls to std::to_string from multiple threads may result in partial serialization of calls. C++17 provides std::to_chars as a higher-performance locale-independent alternative.

[edit] Example

#include #include int main() { for (const double f : {23.43, 1e-9, 1e40, 1e-40, 123456789.0}) std::cout  "std::cout: "  f  '\n'  "to_string: "  std::to_string(f)  "\n\n"; }

std::cout: 23.43 to_string: 23.430000 std::cout: 1e-09 to_string: 0.000000 std::cout: 1e+40 to_string: 10000000000000000303786028427003666890752.000000 std::cout: 1e-40 to_string: 0.000000 std::cout: 1.23457e+08 to_string: 123456789.000000

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std:: to_string

Returns a string with the representation of val.

The format used is the same that printf would print for the corresponding type:

type of val	printf equivalent	description
int	"%d"	Decimal-base representation of val. The representations of negative values are preceded with a minus sign (-).
long	"%ld
long long	"%lld
unsigned	"%u"	Decimal-base representation of val.
unsigned long	"%lu
unsigned long long	"%llu
float	"%f"	As many digits are written as needed to represent the integral part, followed by the decimal-point character and six decimal digits. inf (or infinity) is used to represent infinity. nan (followed by an optional sequence of characters) to represent NaNs (Not-a-Number). The representations of negative values are preceded with a minus sign (-).
double	"%f
long double	"%Lf

Parameters

Return Value

Example

// to_string example // std::cout // std::string, std::to_string int main () < std::string pi = "pi is " + std::to_string(3.1415926); std::string perfect = std::to_string(1+2+4+7+14) + " is a perfect number"; std::cout '\n'; std::cout '\n'; return 0; >

pi is 3.141593 28 is a perfect number 

Exceptions

See also

sprintf Write formatted data to string (function) to_wstring Convert numerical value to wide string (function)

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std::to_string

Может бросить std::bad_alloc из конструктора std::string .

Notes

• С типами с плавающей точкой std::to_string может дать неожиданные результаты, так как количество значащих цифр в возвращаемой строке может быть нулевым, см. Пример.
• Возвращаемое значение может значительно отличаться от того, что выводит std::cout по умолчанию, см. Пример.
• std::to_string опирается на текущую локаль для целей форматирования, и поэтому одновременные вызовы std::to_string из нескольких потоков могут привести к частичной сериализации вызовов. C ++ 17 предоставляет std::to_chars как высокопроизводительную независимую от локали альтернативу.

Example

#include #include int main() < for (const double f : 23.43, 1e-9, 1e40, 1e-40, 123456789.>) std::cout "std::cout: " << f '\n' "to_string: " to_string(f) "\n\n"; >

std::cout: 23.43 to_string: 23.430000 std::cout: 1e-09 to_string: 0.000000 std::cout: 1e+40 to_string: 10000000000000000303786028427003666890752.000000 std::cout: 1e-40 to_string: 0.000000 std::cout: 1.23457e+08 to_string: 123456789.000000

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