std::ceil,std::ceilf,std::ceill(3)

NAME
std::ceil,std::ceilf,std::ceill - std::ceil,std::ceilf,std::ceill

Synopsis
   Defined in header <cmath>
   float ceil ( float num );
   double ceil ( double num ); (until C++23)
   long double ceil ( long double num );
   constexpr /* floating-point-type */ (since C++23)
               ceil ( /* floating-point-type */ num );
   float ceilf( float num ); (1) (2) (since C++11)
                        (constexpr since C++23)
   long double ceill( long double num ); (3) (since C++11)
                        (constexpr since C++23)
   Additional overloads (since C++11)
   Defined in header <cmath>
   template< class Integer > (A) (constexpr since C++23)
   double ceil ( Integer num );
   1-3) Computes the least integer value not less than num.
   The library provides overloads of std::ceil for all cv-unqualified floating-point
   types as the type of the parameter.
   (since C++23)
   A) Additional overloads are provided for all integer types, which are (since C++11)
   treated as double.

Parameters
   num - floating point or integer value

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

Return value
   math-ceil.svg
   num

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 num is ±∞, it is returned unmodified.
     * If num is ±0, it is returned, unmodified.
     * If num is NaN, NaN is returned.

Notes
   FE_INEXACT may be (but is not 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 std::intmax_t), when stored in an
   integer variable. It is for this reason that the return type is floating-point not
   integral.
   This function (for double argument) behaves as if (except for the freedom to not
   raise FE_INEXACT) implemented by the following code:
 #include <cfenv>
 #include <cmath>
 #pragma STDC FENV_ACCESS ON
 double ceil(double x)
 {
     int save_round = std::fegetround();
     std::fesetround(FE_UPWARD);
     double result = std::rint(x); // or std::nearbyint
     std::fesetround(save_round);
     return result;
 }
   The additional overloads are not required to be provided exactly as (A). They only
   need to be sufficient to ensure that for their argument num of integer type,
   std::ceil(num) has the same effect as std::ceil(static_cast<double>(num)).

Example
// Run this code
 #include <cmath>
 #include <iostream>
 int main()
 {
     std::cout << std::fixed
               << "ceil(+2.4) = " << std::ceil(+2.4) << '\n'
               << "ceil(-2.4) = " << std::ceil(-2.4) << '\n'
               << "ceil(-0.0) = " << std::ceil(-0.0) << '\n'
               << "ceil(-Inf) = " << std::ceil(-INFINITY) << '\n';
 }

Output:
 ceil(+2.4) = 3.000000
 ceil(-2.4) = -2.000000
 ceil(-0.0) = -0.000000
 ceil(-Inf) = -inf

See also
   floor
   floorf nearest integer not greater than the given value
   floorl (function)
   (C++11)
   (C++11)
   trunc
   truncf
   truncl nearest integer not greater in magnitude than the given value
   (C++11) (function)
   (C++11)
   (C++11)
   round
   roundf
   roundl
   lround
   lroundf
   lroundl
   llround
   llroundf
   llroundl nearest integer, rounding away from zero in halfway cases
   (C++11) (function)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   nearbyint
   nearbyintf
   nearbyintl nearest integer using current rounding mode
   (C++11) (function)
   (C++11)
   (C++11)
   rint
   rintf
   rintl
   lrint
   lrintf
   lrintl
   llrint
   llrintf nearest integer using current rounding mode with
   llrintl exception if the result differs
   (C++11) (function)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   (C++11)
   C documentation for
   ceil

External links
   Fast ceiling of an integer division — StackOverflow