function     PORM, arg

;+
; NAME:
;	PORM
;
; PURPOSE:
;	Returns "Plus OR Minus" String
;
; SEE ALSO:
;	OROMO
;
; MODIFICATION HISTORY:
;	26 Jul 2007	Written by Mattia Vaccari
;
;	07 Dec 2007	Debugging
;-

if n_elements(arg) eq 0 then begin

  print,'Argument is undefined! Returning blank string...'
  res=''
  goto,FIN

endif else if n_elements(arg) eq 1 then begin

  if arg ge 0 then res = '+' else res = '-'

endif else begin

  res=strarr(n_elements(arg))

  j=where(arg ge 0) & if j[0] ne -1 then res[j]='+'
  j=where(arg lt 0) & if j[0] ne -1 then res[j]='-'

endelse

FIN:

return, res

end