;/* ----------------------------------------------------------------------
; Find the nearest element in an array to the given value.
; This version uses a binary search for speed.
; The array must be sorted for this to work.
;   Input: xx (given value).
;   Input: narr (number of elements in array).
;   Input: arr (the array to be searched).
; Array MUST be sorted, low values to high values.
;*/

function cneari_bs, xx, narr,  arr

; Binary search.
  if (narr le 1L) then return, 0L
  ii=0L
  i1=0L
  i2=narr-1L
  while ((i2-i1) gt 1L) do begin
     ii = (i1+i2)/2
     if (arr[ii] gt xx) then i2=ii else i1=ii
  endwhile
  if (i2 le i1) then printf,-2,"***ERROR: cneari_bs: this should not happen."
  if ( ABS((arr[i1] - xx)) le ABS((arr[i2] - xx)) ) then kk=i1  else kk=i2
  return,kk
end