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) (constexpr since C++23)
std::ldiv_t div( long x, long y ); (2) (constexpr since C++23)
std::lldiv_t div( long long x, long long y ); (3) (since C++11)
(constexpr since C++23)
std::ldiv_t ldiv( long x, long y ); (4) (constexpr since C++23)
std::lldiv_t lldiv( long long x, long long y ); (5) (since C++11)
(constexpr since C++23)
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.

Overload of std::div for std::intmax_t is provided in <cinttypes> if (since C++11)
and only if std::intmax_t is an extended integer type.

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

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>
#include <sstream>
#include <cassert>

std::string euclidean_division_string(int dividend, int divisor)
{
auto dv = std::div(dividend, divisor);
assert(dividend == divisor * dv.quot + dv.rem);
assert(dv.quot == dividend / divisor);
assert(dv.rem == dividend % divisor);

return (std::ostringstream() << std::showpos << dividend << " = "
<< divisor << " * (" << dv.quot << ") "
<< std::showpos << dv.rem).str();
}

std::string itoa(int n, int radix /*[2..16]*/)
{
std::string buf;
std::div_t dv{}; dv.quot = n;
do {
dv = std::div(dv.quot, radix);
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 << euclidean_division_string(369, 10) << '\n'
<< euclidean_division_string(369, -10) << '\n'
<< euclidean_division_string(-369, 10) << '\n'
<< euclidean_division_string(-369, -10) << "\n\n";

std::cout << itoa(12345, 10) << '\n'
<< itoa(-12345, 10) << '\n'
<< itoa(42, 2) << '\n'
<< itoa(65535, 16) << '\n';
}

Output:

+369 = +10 * (+36) +9
+369 = -10 * (-36) +9
-369 = +10 * (-36) -9
-369 = -10 * (+36) -9

12345
-12345
101010
ffff

External links

* Euclidean division