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C Library Functions  - locate (3)

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NAME

locate(3f) - [M_list] finds the index where a string is found or should be in a sorted array (LICENSE:PD)

CONTENTS

Synopsis
Description
Options
Returns
Examples
Author
License

SYNOPSIS

subroutine locate(list,value,place,ier,errmsg)

   character(len=:)|doubleprecision|real|integer,allocatable :: list(:)
   character(len=*)|doubleprecision|real|integer,intent(in)  :: value
   integer, intent(out)                  :: PLACE

   integer, intent(out),optional         :: IER
   character(len=*),intent(out),optional :: ERRMSG

DESCRIPTION

LOCATE(3f) finds the index where the VALUE is found or should be found in an array. The array must be sorted in descending order (highest at top). If VALUE is not found it returns the index where the name should be placed at with a negative sign.

The array and list must be of the same type (CHARACTER, DOUBLEPRECISION, REAL,INTEGER)

OPTIONS

VALUE	the value to locate in the list.
LIST	is the list array.

RETURNS

PLACE	is the subscript that the entry was found at if it is greater than zero(0). If PLACE is negative, the absolute value of PLACE indicates the subscript value where the new entry should be placed in order to keep the list alphabetized.
IER	is zero(0) if no error occurs. If an error occurs and IER is not present, the program is stopped.
ERRMSG	description of any error

EXAMPLES

Find if a string is in a sorted array, and insert the string into the list if it is not present ...

    program demo_locate
    use M_sort, only : sort_shell
    use M_list, only : locate
    implicit none
    character(len=:),allocatable  :: arr(:)
    integer                       :: i

    arr=[character(len=20) :: ’’, ’ZZZ’, ’aaa’, ’b’, ’xxx’ ]
    ! make sure sorted in descending order
    call sort_shell(arr,order=’d’)

    call update(arr,’b’)
    call update(arr,’[’)
    call update(arr,’c’)
    call update(arr,’ZZ’)
    call update(arr,’ZZZZ’)
    call update(arr,’z’)

    contains
    subroutine update(arr,string)
    character(len=:),allocatable :: arr(:)
    character(len=*)             :: string
    integer                      :: place, plus, ii, end
    ! find where string is or should be
    call locate(arr,string,place)
    write(*,*)’for "’//string//’" index is ’,place, size(arr)
    ! if string was not found insert it
    if(place.lt.1)then
       plus=abs(place)
       ii=len(arr)
       end=size(arr)
       ! empty array
       if(end.eq.0)then
          arr=[character(len=ii) :: string ]
       ! put in front of array
       elseif(plus.eq.1)then
          arr=[character(len=ii) :: string, arr]
       ! put at end of array
       elseif(plus.eq.end)then
          arr=[character(len=ii) :: arr, string ]
       ! put in middle of array
       else
          arr=[character(len=ii) :: arr(:plus-1), string,arr(plus:) ]
       endif
       ! show array
       write(*,’("SIZE=",i0,1x,*(a,","))’)end,(trim(arr(i)),i=1,end)
    endif
    end subroutine update
    end program demo_locate

Results

      >  for "b" index is            2           5
      >  for "[" index is           -4           5
      > SIZE=5 xxx,b,aaa,[,ZZZ,
      >  for "c" index is           -2           6
      > SIZE=6 xxx,c,b,aaa,[,ZZZ,
      >  for "ZZ" index is           -7           7
      > SIZE=7 xxx,c,b,aaa,[,ZZZ,,
      >  for "ZZZZ" index is           -6           8
      > SIZE=8 xxx,c,b,aaa,[,ZZZZ,ZZZ,,
      >  for "z" index is           -1           9
      > SIZE=9 z,xxx,c,b,aaa,[,ZZZZ,ZZZ,,

AUTHOR

1989,2017 John S. Urban

LICENSE

Public Domain

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Nemo Release 3.1

locate (3)

February 23, 2025

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