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 | (until C++11) |
The quotient is the result of the expression | (since C++11) |
x, y | - | integer values |
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:
struct div_t { int quot; int rem; };
or.
struct div_t { int rem; int quot; };
struct ldiv_t { long quot; long rem; };
or.
struct ldiv_t { long rem; long quot; };
struct lldiv_t { long long quot; long long rem; };
or.
struct lldiv_t { long long rem; long long quot; };
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.
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.
#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
(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) |
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