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ceil, ceilf, ceill

From cppreference.com

< c‎ | numeric‎ | math

Compiler support

Program utilities

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Strings library

Date and time utilities

Input/output support

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Concurrency support (C11)

Technical Specifications

Common mathematical functions

Floating-point environment (C99)

Pseudo-random number generation

Complex number arithmetic (C99)

Type-generic math (C99)

Bit manipulation (C23)

Checked integer arithmetic (C23)

Common mathematical functions

Functions

Basic operations

abslabsllabsimaxabs

(C99)(C99)

divldivlldivimaxdiv

(C99)(C99)

(C99)

(C99)

(C99)

(C99)

nannanfnanlnandN

(C99)(C99)(C99)(C23)

Maximum/minimum operations

(C99)

(C99)

(C23)

(C23)

(C23)

(C23)

(C23)

(C23)

fmaximum_mag_num

(C23)

fminimum_mag_num

(C23)

Exponential functions

(C23)

(C99)

(C99)

(C23)

(C23)

(C99)

(C99)(C23)

(C23)

(C23)

Power functions

(C99)

(C23)

(C23)

(C99)

(C23)

(C23)

(C23)

Trigonometric and hyperbolic functions

(C23)

(C23)

(C23)

(C23)

(C23)

(C23)

(C23)

(C99)

(C99)

(C99)

Nearest integer floating-point

ceil

roundlroundllround

(C99)(C99)(C99)

(C23)

(C99)

(C99)

rintlrintllrint

(C99)(C99)(C99)

fromfpfromfpxufromfpufromfpx

(C23)(C23)(C23)(C23)

Floating-point manipulation

(C99)(C99)

(C99)(C23)

(C99)

nextafternexttoward

(C99)(C99)

(C23)(C23)

(C99)

(C23)

Narrowing operations

(C23)

(C23)

(C23)

(C23)

(C23)

(C23)

Quantum and quantum exponent

(C23)

(C23)

(C23)

(C23)

Decimal re-encoding functions

(C23)

(C23)

(C23)

(C23)

Total order and payload functions

(C23)

(C23)

(C23)

(C23)

Classification

(C99)

(C23)

(C99)

(C99)

(C99)

(C99)

(C99)

(C23)

(C23)

(C99)

(C99)

(C99)

(C99)

(C99)

(C99)

(C23)

(C23)

Error and gamma functions

(C99)

(C99)

(C99)

(C99)

Types

div_tldiv_tlldiv_timaxdiv_t

(C99)(C99)

float_tdouble_t

(C99)(C99)

_Decimal32_t_Decimal64_t

(C23)(C23)

Macro constants

Special floating-point values

HUGE_VALHUGE_VALFHUGE_VALLHUGE_VALDN

(C99)(C99)(C23)

INFINITYDEC_INFINITY

(C99)(C23)

(C99)(C23)

Arguments and return values

FP_ILOGB0FP_ILOGBNAN

(C99)(C99)

FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN

(C99)(C99)(C99)(C99)(C99)

FP_LLOGB0FP_LLOGBNAN

(C23)(C23)

FP_INT_UPWARDFP_INT_DOWNWARDFP_INT_TOWARDZEROFP_INT_TONEARESTFROMZEROFP_INT_TONEAREST

(C23)(C23)(C23)(C23)(C23)

Error handling

MATH_ERRNOMATH_ERRNOEXCEPT

(C99)(C99)

math_errhandling

(C99)

Fast operation indicators

FP_FAST_FMAFFP_FAST_FMA

(C99)(C99)

FP_FAST_FADDFP_FAST_FADDLFP_FAST_DADDLFP_FAST_DMADDDN

(C23)(C23)(C23)(C23)

FP_FAST_FMULFP_FAST_FMULLFP_FAST_DMULLFP_FAST_DMMULDN

(C23)(C23)(C23)(C23)

FP_FAST_FFMAFP_FAST_FFMALFP_FAST_DFMALFP_FAST_DMFMADN

(C23)(C23)(C23)(C23)

FP_FAST_FMALFP_FAST_FMADN

(C99)(C23)

FP_FAST_FSUBFP_FAST_FSUBLFP_FAST_DSUBLFP_FAST_DMSUBDN

(C23)(C23)(C23)(C23)

FP_FAST_FDIVFP_FAST_FDIVLFP_FAST_DDIVLFP_FAST_DMDIVDN

(C23)(C23)(C23)(C23)

FP_FAST_FSQRTFP_FAST_FSQRTLFP_FAST_DSQRTLFP_FAST_DMSQRTDN

(C23)(C23)(C23)(C23)

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

1 Parameters
2 Return value
3 Error handling
4 Notes
5 Example
6 References
7 See also

[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

[画像: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 <fenv.h>
#include <math.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

Run this code

#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] References

C23 standard (ISO/IEC 9899:2024):

7.12.9.1 The ceil functions (p: TBD)

7.25 Type-generic math <tgmath.h> (p: TBD)

F.10.6.1 The ceil functions (p: TBD)

C17 standard (ISO/IEC 9899:2018):

7.12.9.1 The ceil functions (p: TBD)

7.25 Type-generic math <tgmath.h> (p: TBD)

F.10.6.1 The ceil functions (p: TBD)

C11 standard (ISO/IEC 9899:2011):

7.12.9.1 The ceil functions (p: 251)

7.25 Type-generic math <tgmath.h> (p: 373-375)

F.10.6.1 The ceil functions (p: 526)

C99 standard (ISO/IEC 9899:1999):

7.12.9.1 The ceil functions (p: 231-232)

7.22 Type-generic math <tgmath.h> (p: 335-337)

F.9.6.1 The ceil functions (p: 462-463)

C89/C90 standard (ISO/IEC 9899:1990):

4.5.6.1 The ceil function

[edit] See also

floorfloorffloorl

(C99)(C99)

computes largest integer not greater than the given value
(function) [edit]

trunctruncftruncl

(C99)(C99)(C99)

rounds to nearest integer not greater in magnitude than the given value
(function) [edit]

roundroundfroundllroundlroundflroundlllroundllroundfllroundl

(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)

rounds to nearest integer, rounding away from zero in halfway cases
(function) [edit]

nearbyintnearbyintfnearbyintl

(C99)(C99)(C99)

rounds to an integer using current rounding mode
(function) [edit]

rintrintfrintllrintlrintflrintlllrintllrintfllrintl

(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]

C++ documentation for ceil

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