;+
; NAME:
;       DIFF
; PURPOSE:
;       Returns the difference of the input values
; CALLING SEQUENCE:
;       diff, x
; EXAMPLES:
;       print, diff([0.1, 0.5])
;           prints 0.400000
;       print, diff([0.5, 0.1])
;           prints -0.400000
;       print, diff(minmax(a))
;           prints the difference between the maximum and minimum
;           value of a
; KEYWORDS:
;       NONE
; MODIFICATION HISTORY:
;       Before 05/06/2007 Written by Eduard Westra
;-
FUNCTION diff, x
  IF N_ELEMENTS(x) NE 2 THEN MESSAGE, 'Only an array of two elements can be given as argument for DIFF.'
  RETURN, x[1]-x[0]
END