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std::div, std::ldiv, std::lldiv

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Common mathematical functions
Functions
Basic operations
divldivlldivimaxdiv
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)(C++11)(C++11)
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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 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, long long, std::imaxdiv_t, respectively), returns both as an object of type std::div_t, std::ldiv_t, std::ldiv_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.

[edit] 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.

[edit] Example

#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)];  // the type of the string literal is 
                                                      // const char[17]
    } 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

[edit] See also

remainder of the floating point division operation
(function) [edit]
(C++11)
signed remainder of the division operation
(function) [edit]
(C++11)
signed remainder as well as the three last bits of the division operation
(function) [edit]