;+
; NAME:
;  oclc_epq03_valset
; PURPOSE: (one line)
;  set a value for an array structure
; DESCRIPTION:
;  set a value for an array structure
; CATEGORY:
;  Occultation lightcurve (oclc)
; CALLING SEQUENCE:
;  oclc_epq03_valset,arr,i,val
; INPUTS:
;  arr = either an integer or half-integer indexed array structure
;  i = cell index, integer or half-integer (same as for arr)
; OPTIONAL INPUT PARAMETERS:
;  none
; KEYWORD INPUT PARAMETERS:
;  none
; KEYWORD OUTPUT PARAMETERS:
;  none
; OUTPUTS:
;  arr_i
; COMMON BLOCKS:
;  None
; SIDE EFFECTS:
; RESTRICTIONS:
;  Only change arr if i is in range, and if i indexed 
;  the same way as arr is (eg if arr is tabulated on 
;  bin centers, with arr.istart integer, then i must be
;  an integer.  If arr is tabulated on bin boundaries,
;  with arr.istart a half-integer, then i much be a
;  hald-integer (like 10.5).)  Otherwise exit quietly.
; PROCEDURE:
;  Elliot, Person and Qu 2003, Fig 2
;
; MODIFICATION HISTORY:
;  Written 2006 Aug 23, Leslie Young, SwRI
;-

pro oclc_epq03_valset, arr, i, val

    if is_array(i) then begin
        for ii = 0, n_elements(i) - 1 do begin
            oclc_epq03_valset,arr,i[ii], val[ii]
        end
        return
    end
    
    indx = (i - arr.istart)

    n = n_elements(arr.val)
    
    if indx ge 0 and indx lt n and (round(indx * 2) mod 2 eq 0) then $
      arr.val[round(indx)] = val

end