;+
; NAME:
; is_sorted
;
;
; PURPOSE:
; determine if an array is sorted
;
;
; INPUTS:
; array: the array to test if it is sorted. 
;
;
; OUTPUTS:
; 1-sorted, 0-not sorted
;
;
; EXAMPLE:
; IDL> print, is_sorted([1,2,3,3,4,5,5])
;        1
; IDL> print, is_sorted([1,2,3,3,2,4,5,5])
;        0
;
;
;
; MODIFICATION HISTORY:
;
;       Fri Aug 29 12:46:51 2008, Brian Larsen
;		written and tested
;
;-
FUNCTION is_sorted, array
  IF n_elements(array) EQ 0 THEN BEGIN
     message, 'Must input an array'
  ENDIF
  
  ;; instead of doing the sorting subtract them and see if the sign is
  ;; always the same
  diff = array - array[1:*]
  sign = sign(diff)
  max = max(sign, min = min)
  IF abs(max-min) EQ 2 THEN $
     return, 0 $                 ; array is not sorted
  ELSE return,  1                ; array is sorted

  return, !values.f_nan         ; should neve rget here
END