Manual Reference Pages - lbound (3fortran)

NAME

LBOUND(3) - [ARRAY:INQUIRY] Lower dimension bounds of an array

SYNOPSIS

result = lbound(array [,dim] [,kind] )

         elemental TYPE(kind=KIND) function lbound(array,dim,kind)

          TYPE(kind=KIND),intent(in)           :: array(..)
          integer(kind=**),intent(in),optional :: dim
          integer(kind=**),intent(in),optional :: kind

CHARACTERISTICS

o ARRAY shall be assumed-rank or an array, of any type. It cannot be an unallocated allocatable array or a pointer that is not associated.

o DIM shall be a scalar integer. The corresponding actual argument shall not be an optional dummy argument, a disassociated pointer, or an unallocated allocatable.

o KIND an integer initialization expression indicating the kind parameter of the result.

o The return value is of type integer and of kind KIND. If KIND is absent, the return value is of default integer kind. The result is scalar if DIM is present; otherwise, the result is an array of rank one and size n, where n is the rank of ARRAY.

o a kind designated as ** may be any supported kind for the type

DESCRIPTION

LBOUND(3) returns the lower bounds of an array, or a single lower bound along the DIM dimension.

OPTIONS

o ARRAY : Shall be an array, of any type.

o DIM : Shall be a scalar integer. If DIM is absent, the result is an array of the upper bounds of ARRAY.

o KIND : An integer initialization expression indicating the kind parameter of the result.

RESULT

If DIM is absent, the result is an array of the lower bounds of ARRAY.
If DIM is present, the result is a scalar corresponding to the lower bound of the array along that dimension. If ARRAY is an expression rather than a whole array or array structure component, or if it has a zero extent along the relevant dimension, the lower bound is taken to be

1.
    NOTE1

    If **array** is assumed-rank and has rank zero, **dim** cannot be
    present since it cannot satisfy the requirement **1 <= dim <= 0**.

EXAMPLES

Note that in my opinion this function should not be used on assumed-size arrays or in any function without an explicit interface. Errors can occur if there is no interface defined.

Sample program

    ! program demo_lbound
    module m_bounds
    implicit none
     contains
        subroutine msub(arr)
           !!integer,intent(in) :: arr(*)  ! cannot be assumed-size array
           integer,intent(in) :: arr(:)
           write(*,*)’MSUB: LOWER=’,lbound(arr), &
           & ’UPPER=’,ubound(arr), &
           & ’SIZE=’,size(arr)
        end subroutine msub
     end module m_bounds

     program demo_lbound
     use m_bounds, only : msub
     implicit none
     interface
        subroutine esub(arr)
        integer,intent(in) :: arr(:)
        end subroutine esub
     end interface
     integer :: arr(-10:10)
        write(*,*)’MAIN: LOWER=’,lbound(arr), &
        & ’UPPER=’,ubound(arr), &
        & ’SIZE=’,size(arr)
        call csub()
        call msub(arr)
        call esub(arr)
     contains
    subroutine csub
       write(*,*)’CSUB: LOWER=’,lbound(arr), &
       & ’UPPER=’,ubound(arr), &
       & ’SIZE=’,size(arr)
    end subroutine csub
    end

     subroutine esub(arr)
     implicit none
     integer,intent(in) :: arr(:)
        ! WARNING: IF CALLED WITHOUT AN EXPLICIT INTERFACE
        ! THIS WILL GIVE UNDEFINED ANSWERS (like 0,0,0)
        write(*,*)’ESUB: LOWER=’,lbound(arr), &
        & ’UPPER=’,ubound(arr), &
        & ’SIZE=’,size(arr)
     end subroutine esub

    !end program demo_lbound

Results:

       MAIN: LOWER=         -10 UPPER=          10 SIZE=          21
       CSUB: LOWER=         -10 UPPER=          10 SIZE=          21
       MSUB: LOWER=           1 UPPER=          21 SIZE=          21
       ESUB: LOWER=           1 UPPER=          21 SIZE=          21

STANDARD

Fortran 95 , with KIND argument - Fortran 2003

o	SIZE(3) - Determine the size of an array
o	RANK(3) - Rank of a data object
o	SHAPE(3) - Determine the shape of an array
o	UBOUND(3) - Upper dimension bounds of an array

o	ARRAY shall be assumed-rank or an array, of any type. It cannot be an unallocated allocatable array or a pointer that is not associated.
o	DIM shall be a scalar integer. The corresponding actual argument shall not be an optional dummy argument, a disassociated pointer, or an unallocated allocatable.
o	KIND an integer initialization expression indicating the kind parameter of the result.
o	The return value is of type integer and of kind KIND. If KIND is absent, the return value is of default integer kind. The result is scalar if DIM is present; otherwise, the result is an array of rank one and size n, where n is the rank of ARRAY.
o	a kind designated as ** may be any supported kind for the type

o	ARRAY : Shall be an array, of any type.
o	DIM : Shall be a scalar integer. If DIM is absent, the result is an array of the upper bounds of ARRAY.
o	KIND : An integer initialization expression indicating the kind parameter of the result.

o	ALLOCATED(3) - Status of an allocatable entity
o	IS_CONTIGUOUS(3) - Test if object is contiguous

o	STORAGE_SIZE(3) - Storage size in bits
o	BIT_SIZE(3) - Bit size inquiry function
o	BTEST(3) - Tests a bit of an integer value.