FUNCTION     MAGSUM, ARG, WC=WC

;+
; NAME:
;	MAGSUM
;
; PURPOSE:
;	Sum magnitudes (companion routine to MAGERRSUM)
;
; MODIFICATION HISTORY:
;	27 Jul 2007	Written by Mattia Vaccari
;-

if not(keyword_set(wc)) then wc=99.0

if n_elements(arg) eq 0 then begin

  print,'Argument is undefined! Returning -1...'
  res=-1
  goto,FIN

endif else if n_elements(arg) eq 1 then begin

  print,'Argument has only one element! Returning argument...'
  res=arg
  goto,FIN

endif

res=-1.0

;j=where(arg ne wc)
j=where(abs(arg-wc) gt 1.e-3)

;if (where(arg ne wc))[0] ne -1 then begin
if j[0] ne -1 then begin
for i=0,n_elements(j)-1 do begin
if res eq -1.0 then res=arg[j[i]] else res=-2.5*alog10(10.^(-0.4*res)+10.^(-0.4*arg[j[i]]))
endfor
endif else print,'No Valid Arguments! Returning -1...'

;if res eq wc then res=-1.0
if abs(res-wc) lt 1.e-3 then res=-1.0

FIN:

return, res

end