function sgn, x

;+
; NAME:
;  sgn
; PURPOSE: (one line)
;  return the sign of a number or list
; DESCRIPTION:
; CATEGORY:
;  Math
; CALLING SEQUENCE:
;  y = sgn(x)
; INPUTS:
;  x - argument
; OPTIONAL INPUT PARAMETERS:
;  none
; KEYWORD INPUT PARAMETERS:
;  none
; KEYWORD OUTPUT PARAMETERS:
;  none
; OUTPUTS:
;  exp(x)-1
; COMMON BLOCKS:
;  None
; SIDE EFFECTS:
; RESTRICTIONS:
;  None
; PROCEDURE:
; MODIFICATION HISTORY:
;  Written 2002 August, by Leslie Young, SwRI
;-

  return, (x gt 0) + (x ge 0) - 1

end