std::div, std::ldiv, std::lldiv, std::imaxdiv - cppreference.com (original) (raw)
| Defined in header | ||
|---|---|---|
| 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 | ||
| 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.
| 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
[edit] 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; };
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 #include #include #include #include #include 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