Manual Reference Pages - ceiling (3fortran)
CEILING(3) - [NUMERIC] returns the least integer greater than or equal to A.
SYNOPSIS
result = ceiling(a [,kind])
elemental integer(KIND) function ceiling(a,KIND)real(kind=**),intent(in) :: a integer,intent(in),optional :: KIND
CHARACTERISTICS
o A is of type real o if present KIND is a scalar integer constant expression that specifies the kind of the result. o the result is integer. It is default kind if KIND is not specified
DESCRIPTION
CEILING(3) returns the least integer greater than or equal to A.
On the number line -n <-- 0 -> +n the value returned is always at or to the right of the input value.
For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.
The input value may be too large to store the result in an integer type. To avoid an overflow (which produces an undefined result), an application should perform a range check on the input value before using ceiling(3).
OPTIONS
o A : A real value to produce a ceiling for. o KIND : indicates the kind parameter of the result.
RESULT
The result will be the integer value equal to A or the least integer greater than A if the input value is not equal to a whole number.
If A is equal to a whole number, the returned value is INT(A).
The result is undefined if it cannot be represented in the specified integer type.
EXAMPLES
Sample program:
program demo_ceiling implicit none ! just a convenient format for a list of integers character(len=*),parameter :: gen=’(1x,*(g0:,1x))’ real :: x real :: y real,parameter :: arr(*)=[ & & -2.7, -2.5, -2.2, -2.0, -1.5, & & -1.0, -0.5, 0.0, +0.5, +1.0, & & +1.5, +2.0, +2.2, +2.5, +2.7 ] integer :: i integer :: ierr character(len=80) :: message print *, ’Basic Usage’ x = 63.29 y = -63.59 print gen, ceiling(x), ceiling(y) ! note the result was the next integer larger to the rightResults:print *, ’Whole Numbers’ ! real values equal to whole numbers x = 63.0 y = -63.0 print gen, ceiling(x), ceiling(y)
print *, ’Elemental’ ! (so an array argument is allowed) print gen , ceiling(arr)
print *, ’Advanced Usage’ ! Dealing with large magnitude values print ’(a)’,[character(len=80):: & ’Limits ’,& ’You only care about Limits if you are using values near or above ’,& ’the limits of the integer type you are using (see huge(3)). ’,& ’’,& ’Surprised by some of the following results? ’,& ’What do real values clearly out of the range of integers return? ’,& ’What do values near the end of the range of integers return? ’,& ’The standard only specifies what happens for representable values’,& ’in the range of integer values. ’,& ’’,& ’It is common but not required that if the input is out of range ’,& ’and positive the result is -huge(0) and -huge(0)-1 if negative. ’,& ’Note you are out of range before you get to real(huge(0)). ’,& ’’ ] print gen , ’For reference: huge(0)=’,huge(0),’-huge(0)-1=’,-huge(0)-1
x=huge(0) call displayx()
x=2*x call displayx()
x=-huge(0)-1 call displayx()
x=2*x call displayx()
print gen , repeat(’=’,80)
contains
subroutine displayx() use,intrinsic :: iso_fortran_env, only: int8,int16,int32,int64 print gen , repeat(’=’,80) print gen , ’x=’,x,’ spacing=’,spacing(x) print gen , ’ ceiling(x):’,ceiling(x) print gen , ’ ceiling(x,kind=int64):’,ceiling(x,kind=int64) print gen , ’ ceiling_robust(x):’,ceiling_robust(x,ierr,message) if(ierr.ne.0)then print gen, ierr,’=>’,trim(message) endif end subroutine displayx
elemental impure function ceiling_robust(x,ierr,message) ! return the least integer >= x use,intrinsic :: iso_fortran_env, only: int8,int16,int32,int64 use,intrinsic :: iso_fortran_env, only: real32,real64,real128 real,intent(in) :: x integer,intent(out),optional :: ierr character(len=*),intent(out),optional :: message character(len=80) :: message_local integer :: ceiling_robust integer :: ierr_local ierr_local=0 message_local=’’ ! allow -huge(0)-1 or not? if(spacing(x) > 128)then ! bounds checking if(x.ge.0)then write(message_local,*)’<ERROR>X=’,x,’ >=’,anint(real(huge(0))) ierr_local=1 ceiling_robust=huge(0) else ierr_local=2 ceiling_robust=-huge(0)-1 write(message_local,*)’<ERROR>X=’,x,’ <=’,anint(real(-huge(0)-1)) endif else ! used to use a computed goto to do this! ceiling_robust = int(x) if (x > 0.0) then if (real(ceiling_robust) < x)then ceiling_robust = ceiling_robust + 1 endif endif endif if(present(ierr))then ierr=ierr_local elseif(ierr_local.ne.0)then stop message_local endif if(present(message))then message=message_local endif end function ceiling_robust
end program demo_ceiling
> Basic Usage > 64 -63 > Whole Numbers > 63 -63 > Elemental > -2 -2 -2 -2 -1 -1 0 0 1 1 2 2 3 3 3 > Limits > > Surprised by some of the following results? > What do real values clearly out of the range of integers return? > What do values near the end of the range of integers return? > The standard only specifies what happens for representable values > in the range of integer values. > > It is common but not required that if the input is out of range > and positive the result is -huge(0) and -huge(0)-1 if negative. > Note you are out of range before you get to real(huge(0)). > > For reference: huge(0)= 2147483647 -huge(0)-1= -2147483648 > ====================================================================== > x= 0.214748365E+10 spacing= 256.000000 > ceiling(x): -2147483647 > ceiling(x,kind=int64): 2147483648 > ceiling_robust(x): 2147483647 > 1 => <ERROR>X= 2.14748365E+09 >= 2.14748365E+09 > ====================================================================== > x= 0.429496730E+10 spacing= 512.000000 > ceiling(x): -2147483647 > ceiling(x,kind=int64): 4294967296 > ceiling_robust(x): 2147483647 > 1 => <ERROR>X= 4.29496730E+09 >= 2.14748365E+09 > ====================================================================== > x= -0.214748365E+10 spacing= 256.000000 > ceiling(x): -2147483648 > ceiling(x,kind=int64): -2147483648 > ceiling_robust(x): -2147483648 > 2 => <ERROR>X= -2.14748365E+09 <= -2.14748365E+09 > ====================================================================== > x= -0.429496730E+10 spacing= 512.000000 > ceiling(x): -2147483648 > ceiling(x,kind=int64): -4294967296 > ceiling_robust(x): -2147483648 > 2 => <ERROR>X= -4.29496730E+09 <= -2.14748365E+09 > ======================================================================
STANDARD
Fortran 95
SEE ALSO
FLOOR(3), NINT(3)
AINT(3), ANINT(3), INT(3), SELECTED_INT_KIND(3)
NEAREST(3), SPACING(3), EPSILON(3)
Fortran intrinsic descriptions (license: MIT) @urbanjost
| Nemo Release 3.1 | ceiling (3fortran) | November 02, 2024 |
