std::div,std::ldiv,std::lldiv (3) - Linux Manuals

std::div,std::ldiv,std::lldiv: std::div,std::ldiv,std::lldiv

NAME

std::div,std::ldiv,std::lldiv - std::div,std::ldiv,std::lldiv

Synopsis

Defined in header <cstdlib>
std::div_t div( int x, int y ); (1)
std::ldiv_t div( long x, long y ); (2)
std::lldiv_t div( long long x, long long y ); (3) (since C++11)
std::ldiv_t ldiv( long x, long y ); (4)
std::lldiv_t lldiv( long long x, long long y ); (5) (since C++11)
Defined in header <cinttypes>
std::imaxdiv_t div( std::intmax_t x, std::intmax_t y ); (6) (since C++11)
std::imaxdiv_t imaxdiv( std::intmax_t x, std::intmax_t y ); (7) (since C++11)

Computes both the quotient and the remainder of the division of the numerator x by the denominator y

The quotient is the algebraic quotient with any fractional part discarded (truncated towards zero). The remainder is such that quot * y + rem == x. (until C++11)
The quotient is the result of the expression x/y. The remainder is the result of the expression x%y. (since C++11)

Parameters

x, y - integer values

Return value

If both the remainder and the quotient can be represented as objects of the corresponding type (int, long, long long, std::imaxdiv_t, respectively), returns both as an object of type std::div_t, std::ldiv_t, std::lldiv_t, std::imaxdiv_t defined as follows:

 std::div_t

  struct div_t { int quot; int rem; };

or

  struct div_t { int rem; int quot; };

 std::ldiv_t

  struct ldiv_t { long quot; long rem; };

or

  struct ldiv_t { long rem; long quot; };

 std::lldiv_t

  struct lldiv_t { long long quot; long long rem; };

or

  struct lldiv_t { long long rem; long long quot; };

 std::imaxdiv_t

  struct imaxdiv_t { std::intmax_t quot; std::intmax_t rem; };

or

  struct imaxdiv_t { std::intmax_t rem; std::intmax_t quot; };

If either the remainder or the quotient cannot be represented, the behavior is undefined.

Notes

Until C++11, the rounding direction of the quotient and the sign of the remainder in the built-in_division_and_remainder_operators was implementation-defined if either of the operands was negative, but it was well-defined in std::div.
On many platforms, a single CPU instruction obtains both the quotient and the remainder, and this function may leverage that, although compilers are generally able to merge nearby / and % where suitable.

Example

// Run this code

  #include <string>
  #include <cmath>
  #include <cstdlib>
  #include <iostream>

  std::string itoa(int n, int base)
  {
      std::string buf;
      std::div_t dv{}; dv.quot = n;
      do {
          dv = std::div(dv.quot, base);
          buf += "0123456789abcdef"[std::abs(dv.rem)]; // string literals are arrays
      } while(dv.quot);
      if(n<0) buf += '-';
      return {buf.rbegin(), buf.rend()};
  }

  int main()
  {
      std::cout << itoa(12345, 10) << '\n'
                << itoa(-12345, 10) << '\n'
                << itoa(65535, 16) << '\n';
  }

Output:

  12345
  -12345
  ffff