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ceil, ceilf, ceill

From cppreference.com
< c‎ | numeric‎ | math
 
 
 
Common mathematical functions
Functions
Basic operations
(C99)
(C99)
(C99)
(C99)
(C99)
(C99)(C99)(C99)
Exponential functions
(C99)
(C99)
(C99)
(C99)
Power functions
(C99)
(C99)
Trigonometric and hyperbolic functions
(C99)
(C99)
(C99)
Error and gamma functions
(C99)
(C99)
(C99)
(C99)
Nearest integer floating point operations
ceil
(C99)(C99)(C99)
(C99)
(C99)(C99)(C99)
Floating point manipulation functions
(C99)(C99)
(C99)
(C99)
Classification
(C99)
(C99)
(C99)
Macro constants
 
Defined in header <math.h>
float       ceilf( float arg );
(1) (since C99)
double      ceil( double arg );
(2)
long double ceill( long double arg );
(3) (since C99)
Defined in header <tgmath.h>
#define ceil( arg )
(4) (since C99)
1-3) Computes the smallest integer value not less than arg.
4) Type-generic macro: If arg has type long double, ceill is called. Otherwise, if arg has integer type or the type double, ceil is called. Otherwise, ceilf is called.

Contents

[edit] Parameters

arg - floating point value

[edit] Return value

If no errors occur, the smallest integer value not less than arg, that is ⌈arg⌉, is returned.

Return value
math-ceil.svg
Argument

[edit] Error handling

Errors are reported as specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

  • The current rounding mode has no effect.
  • If arg is ±∞, it is returned unmodified
  • If arg is ±0, it is returned, unmodified
  • If arg is NaN, NaN is returned

[edit] Notes

FE_INEXACT may be (but isn't required to be) raised when rounding a non-integer finite value.

The largest representable floating-point values are exact integers in all standard floating-point formats, so this function never overflows on its own; however the result may overflow any integer type (including intmax_t), when stored in an integer variable.

This function (for double argument) behaves as if (except for the freedom to not raise FE_INEXACT) implemented by

#include <math.h>
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
double ceil(double x)
{
    double result;
    int save_round = fegetround();
    fesetround(FE_UPWARD);
    result = rint(x); // or nearbyint 
    fesetround(save_round);
    return result;
}

[edit] Example

#include <math.h>
#include <stdio.h>
int main(void)
{
    printf("ceil(+2.4) = %+.1f\n", ceil(2.4));
    printf("ceil(-2.4) = %+.1f\n", ceil(-2.4));
    printf("ceil(-0.0) = %+.1f\n", ceil(-0.0));
    printf("ceil(-Inf) = %+f\n",   ceil(-INFINITY));
}

Possible output:

ceil(+2.4) = +3.0
ceil(-2.4) = -2.0
ceil(-0.0) = -0.0
ceil(-Inf) = -inf

[edit] See also

computes largest integer not greater than the given value
(function) [edit]
(C99)(C99)(C99)
rounds to nearest integer not greater in magnitude than the given value
(function) [edit]
(C99)(C99)(C99)
rounds to nearest integer, rounding away from zero in halfway cases
(function) [edit]
rounds to an integer using current rounding mode
(function) [edit]
(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)
rounds to an integer using current rounding mode with
exception if the result differs
(function) [edit]