std:: div, std:: ldiv, std:: lldiv, std:: imaxdiv
|
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)
(constexpr since C++23) |
|
std
::
imaxdiv_t
imaxdiv
(
std::
intmax_t
x,
std::
intmax_t
y
)
;
|
(7) |
(since C++11)
(constexpr since C++23) |
Computes both the quotient and the remainder of the division of the numerator x by the denominator y .
|
6,7)
Overload of
std::div
for
std::intmax_t
is provided in
<cinttypes>
if and only if
std::intmax_t
is an
extended integer type
.
|
(since C++11) |
|
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::intmax_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
CWG issue 614
was resolved (
N2757
), 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
#include <cassert> #include <cmath> #include <cstdlib> #include <iostream> #include <sstream> #include <string> std::string division_with_remainder_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); auto sign = [](int n){ return n > 0 ? 1 : n < 0 ? -1 : 0; }; assert((dv.rem == 0) or (sign(dv.rem) == sign(dividend))); 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 << division_with_remainder_string(369, 10) << '\n' << division_with_remainder_string(369, -10) << '\n' << division_with_remainder_string(-369, 10) << '\n' << division_with_remainder_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
See also
|
(C++11)
(C++11)
|
remainder of the floating point division operation
(function) |
|
(C++11)
(C++11)
(C++11)
|
signed remainder of the division operation
(function) |
|
(C++11)
(C++11)
(C++11)
|
signed remainder as well as the three last bits of the division operation
(function) |
|
C documentation
for
div
|
|
External links
| 1. | Euclidean division — From Wikipedia. |
| 2. | Modulo (and Truncated division) — From Wikipedia. |