fltpnt.h

• copysign
• nearbyint
• nextafter
• remainder
• remquo
• rint
• rndtol, rndtonl
• round
• scalb
• trunc

---

copysign

Header

fltpnt.h

Prototype

double copysign(double x, double y);
float copysignf(float x, float y);
long double copysignl(long double x, long double y);

Description

These functions copy the sign bit of y into x, but do not trigger a signalling NaN.

Return Value

Returns x with the same sign as y.

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

Example

/* Example for copysign */

#include <stdio.h>
#include <fltpnt.h>

void main()
{
  double result, x, y;

  x = 0.34;
  y = -1.9;
  result = copysign(x, y);
  printf("The result is %g\n", result);
}

Output

The result is -0.34

---

nearbyint

Header

fltpnt.h

Prototype

double nearbyint(double x);
float nearbyintf(float x);
long double nearbyintl(long double x);

Description

Rounds x to the nearest integer value, using the current rounding mode. Unlike the rint functions, nearbyint does not raise the FE_INEXACT exception.

Return Value

x rounded to an integer value.

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

See Also

ceil floor rint rndtol rndtonl round trunc

Example

/* Example of nearbyint
   Also demonstrates nearbyintf
*/

#include <stdlib.h>
#include <stdio.h>
#include <fltpnt.h>

void main()
{
   double d;
   printf("Enter a double: ");
   scanf("%lg", &d);
   printf("\nnearbyint(%g)=%g\n",
          d, nearbyint (d));
}

Output

Enter a double: 3.14
nearbyint(3.14)= 3

---

nextafter

Header

fltpnt.h

Prototype

double nextafter(double x, double y);
float nextafterf(float x, float y)
long double nextafterl(long double x, long double y);

Description

Calculates the next representable value after x in the direction of y.

Return Value

If y is greater than x, the result will be the next largest floating-point value; if y is less than x, the result will be the next smallest value. If x and y are equal, the result is x. The FE_INEXACT and FE_OVERFLOW exceptions will be raised if x is finite and the function result is infinite. The FE_INEXACT and FE_UNDERFLOW exceptions will be raised if the function value is subnormal, and x is not equal to y.

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

Example

/* Example for nextafter
   Also demonstrates nextafterf
*/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <fltpnt.h>

void main()
{
 double d1, d2, r;
 printf("Enter two doubles: ");
 scanf("%lg %lg", &d1, &d2);

 r = nextafter(d1, d2);
 printf("nextafter(%g, %g)=%. 16f\n",
    d1, d2, r);
}

Output

Enter two doubles: 1 2
nextafter(1, 2)= 1.0000000000000002

---

remainder

Header

fltpnt.h
fltenv.h (required for exception values)

Prototype

double remainder(double x, double y);
float remainderf(float x, float y);
long double remainderl(long double x, long double y);

Description

Computes the remainder of x / y, following the IEEE standard.

Return Value

The value of x - y * n, where n is the integer nearest the exact value of x / y. If |n - x / y| == 0.5, n is even. If the result is zero, it has the same sign as x. Otherwise, the sign of the result is the sign of x / y. Precision mode has no affect on the remainder functions.

Special Results

x	y	return value	invalid?
±0.0	not 0.0	±0.0	no
±INFINITY	anything	NAN	yes
anything	±0.0	NAN	yes
!= ±INFINITY	±INFINITY	x	no

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

See Also

div ldiv fmod remquo

Example

/* Example for remainer
   Also demonstrates remainderf
*/

#include <stdio.h>
#include <stdlib.h>
#include <fltpnt.h>

void main()
{
 double d1, d2, r;
 printf("Enter two doubles: ");
 scanf("%lg %lg", &d1, &d2);

 r = remainder(d1, d2);
 printf("remainder(%g, %g)=%g\n",
      d1, d2, r);
}

Output

Enter two doubles: 16 9
remainder(16, 9)= 7

---

remquo

Header

fltpnt.h
fltenv.h (required for exception values)

Prototype

double remquo(double x, double y, int * quo);
float remquof(float x, float y, int * quo);
long double remquol(long double x, long double y, int * quo);

Description

Calculates the same value as the remainder functions, and places the integral quotient of x / y into the int pointed to by quo. For an x value much larger than y, this function may be unable to return an exact value for the quotient.

Return Value

The same value as remainder(x, y).

Special Results

x	y	returns	quo	invalid?
±0.0	not 0.0	±0.0	0.0	no
±INFINITY	anything	NAN	?	yes
anything	±0.0	NAN	?	yes
!= ±INFINITY	±INFINITY	x	?	no

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

See Also

remainder

Example

/* Example for remquo
   Also demonstrates remquof
*/

#include <stdio.h>
#include <stdlib.h>
#include <fltpnt.h>

void main()
{
 double d1, d2, r;
 int q;

 printf("Enter two doubles: ");
 scanf("%lg %lg", &d1, &d2);

 r = remquo(d1, d2, &q);
 printf("remquo(%g, %g, &q)=%g\nq = %d",
        d1, d2, r, q);
}

Output

Enter two doubles: 16 9
remquo(16, 9, &q)= 7
q = 1

---

rint

Header

math.h

Prototype

double rint(double x);
float rintf(float x);
long double rintl(long double x);

Description

Rounds x to the nearest integer value, using the current rounding mode. If the return value is not equal to x, the FE_INEXACT exception is raised. The nearbyint functions perform the same operation, but do not set the FE_INEXACT exception.

Return Value

x rounded to an integer value.

Compatibility

ANSI C99 7.12.9.4, DOS, Windows 3.x, Phar Lap, DOSX, Win32

See Also

rndtol rndtonl round

Example

/* Example of rint
   Also demonstrates rintf
*/

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

void main()
{
 double d;

 printf("Enter a double: ");
 scanf("%lg", &d);
 printf("\nrint(%g) = %g\n",
        d, rint(d));
}

Output

Enter a double: 3.14

rint(3.14) = 3

---

rndtol

Header

fltpnt.h

Prototype

long rndtol(double x);
long rndtonl(double x);

Description

Returns x rounded to a long value. If the integer value of x is greater than the maximum value of a long, the result is indeterminate.

The rndtol function uses the current rounding mode. The rndtonl function uses the FE_TONEAREST rounding mode.

Return Value

x rounded to a long.

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

See Also

rint round trunc

Example

/* Example of rndtol */

#include <stdlib.h>
#include <stdio.h>
#include <fltpnt.h>

void main()
{
 double d;

 printf("Enter a double: ");
 scanf("%lg", &d);
 printf("\nrndtol(%g)=%ld\n",
    d, rndtol(d));
}

/* Example of rndtonl */

#include <stdlib.h>
#include <stdio.h>
#include <fltpnt.h>

void main()
{
 double d;
 printf("Enter a double: ");
 scanf("%lg", &d);
 printf("\nrndtonl(%g)=%ld\n",
        d, rndtonl(d));
}

Output

Enter a double: 3.14

rndtol(3.14)= 3

Enter a double: 3.14

rndtonl(3.14)= 3

---

round

Header

fltpnt.h

Prototype

double round(double x);
float roundf(float x);
long double roundl(long double x);

Description

Return the value of x rounded to the nearest integer. If the fractional part of x is exactly 0.5, the return value is rounded to the even integer.

Return Value

x rounded to the nearest integer value.

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

See Also

rint rndtol rndtonl

Example

/* Example of round
   Also demonstrates roundf
*/

#include <stdlib.h>
#include <stdio.h>
#include <fltpnt.h>

void main()
{
 double d;
 printf("Enter a double: ");
 scanf("%lg", &d);
 printf("\nround(%g)=%g\n",
      d, round (d));
}

Output

Enter a double: 3.14

round(3.14)= 3

---

scalb

Header

fltpnt.h

Prototype

double scalb(double x, long n);
float scalbf(float x, long n);
long double scalbl(long double x, long n);

Description

Calculates x * FLT_RADIXⁿ efficiently, without calculating FLT_RADIX n explicitly. scalb handles underflow and overflow in the same fashion as the basic arithmetic operators.

Return Value

The value of x * FLT_RADIXⁿ .

Special Results

x	return value
±INFINITY	±INFINITY
±0.0	±0.0

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

Example

/* Example of scalb
   Also demonstrates scalbf
*/

#include <stdlib.h>
#include <stdio.h>
#include <fltpnt.h>
#include <float.h>

void main()
{
 double d;
 long l;

 printf("Enter a double and an int: ");
 scanf("%lg %ld", &d, &l);
 printf("\n%g * %d^%ld=%g\n",
        d, FLT_RADIX, l, scalb(d, l));
}

Output

Enter a double and an int: 10 6

10 * 2^6= 640

---

trunc

Header

fltpnt.h

Prototype

double trunc(double x);
float truncf(float x);
long double truncl(long double x);

Description

Returns the integer portion of x, dropping the fractional portion. This is also know as "chop" rounding.

Return Value

x without its fractional part.

Compatibility

DOS Windows 3.x Phar Lap DOSX Win32

See Also

ceil floor rint rndtol rndtonl round

Example

/* Example of trunc
   Also demonstrates truncl, truncf
*/

#include <stdlib.h>
#include <stdio.h>
#include <fltpnt.h>

void main()
{
 double d;

 printf("Enter a double: ");
 scanf("%lg", &d);
 printf("\ntrunc(%g)=%g\n",
      d, trunc (d));
}

Output

Enter a double: 3.14

trunc(3.14)= 3

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