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div, ldiv, lldiv, imaxdiv

From cppreference.com
< c‎ | numeric‎ | math
 
 
 
Common mathematical functions
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divldivlldivimaxdiv
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div_tldiv_tlldiv_timaxdiv_t
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Defined in header <stdlib.h>
div_t     div( int x, int y );
(1)
ldiv_t    ldiv( long x, long y );
(2)
lldiv_t   lldiv( long long x, long long y );
(3) (since C99)
Defined in header <inttypes.h>
imaxdiv_t imaxdiv( intmax_t x, intmax_t y );
(4) (since C99)

Computes both the quotient and the remainder of the division of the numerator x by the denominator y.

Computes quotient and remainder simultaneously. The quotient is the algebraic quotient with any fractional part discarded (truncated towards zero). The remainder is such that quot * y + rem == x.

(until C99)

Computes the quotient (the result of the expression x / y) and remainder (the result of the expression x % y) simultaneously.

(since C99)

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, intmax_t, respectively), returns both as an object of type div_t, ldiv_t, lldiv_t, imaxdiv_t defined as follows:

div_t

struct div_t { int quot; int rem; };

or

struct div_t { int rem; int quot; };

ldiv_t

struct ldiv_t { long quot; long rem; };

or

struct ldiv_t { long rem; long quot; };

lldiv_t

struct lldiv_t { long long quot; long long rem; };

or

struct lldiv_t { long long rem; long long quot; };

imaxdiv_t

struct imaxdiv_t { intmax_t quot; intmax_t rem; };

or

struct imaxdiv_t { intmax_t rem; intmax_t quot; };

If either the remainder or the quotient cannot be represented, the behavior is undefined.

[edit] Notes

Until C99, 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 div and ldiv.

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 <assert.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <limits.h>
 
void reverse(char* first, char* last)
{
    for (--last; first < last; ++first, --last)
    {
        char c = *last;
        *last = *first;
        *first = c;
    }
}
 
// demo only: does not check for buffer overflow
char* itoa(int n, int base, char* buf)
{
    assert(2 <= base && base <= 16);
    div_t dv = {.quot = n};
    char* p = buf;
    do
    {
        dv = div(dv.quot, base);
        *p++ = "0123456789abcdef"[abs(dv.rem)];
    }
    while(dv.quot);
    if (n < 0)
        *p++ = '-';
    *p = '\0';
    reverse(buf, p);
    return buf;
}
 
int main(void)
{
    char buf[100];
    printf("%s\n", itoa(0, 2, buf));
    printf("%s\n", itoa(007, 3, buf));
    printf("%s\n", itoa(12346, 10, buf));
    printf("%s\n", itoa(-12346, 10, buf));
    printf("%s\n", itoa(-42, 2, buf));
    printf("%s\n", itoa(INT_MAX, 16, buf));
    printf("%s\n", itoa(INT_MIN, 16, buf));
}

Possible output:

0
21
12346
-12346
-101010
7fffffff
-80000000

[edit] References

  • C17 standard (ISO/IEC 9899:2018):
  • 7.8.2.2 The imaxdiv function (p: 159)
  • 7.22.6.2 The div, ldiv and lldiv functions (p: 259)
  • C11 standard (ISO/IEC 9899:2011):
  • 7.8.2.2 The imaxdiv function (p: 219)
  • 7.22.6.2 The div, ldiv and lldiv functions (p: 356)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.8.2.2 The imaxdiv function (p: 200)
  • 7.20.6.2 The div, ldiv and lldiv functions (p: 320)
  • C89/C90 standard (ISO/IEC 9899:1990):
  • 4.10 div_t, ldiv_t
  • 4.10.6.2 The div function
  • 4.10.6.4 The ldiv function

[edit] See also

(C99)(C99)
computes remainder of the floating-point division operation
(function) [edit]
computes signed remainder of the floating-point division operation
(function) [edit]
(C99)(C99)(C99)
computes signed remainder as well as the three last bits of the division operation
(function) [edit]

[edit] External links

  Euclidean Division