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(longlong x, longlong 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(longlong x, longlong 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) |
Contents |
[edit]Parameters
| x, y | - | integer values |
[edit]Return value
If both the remainder and the quotient can be represented as objects of the corresponding type (int, long, longlong, 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 {longlong quot;longlong rem;};
or
struct lldiv_t {longlong rem;longlong 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.
[edit]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.
[edit]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
[edit]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 | |
[edit]External links
| 1. | Euclidean division — From Wikipedia. |
| 2. | Modulo (and Truncated division) — From Wikipedia. |
