PRO cutcommand, widcommand, toread, coef, numberofread, operation, nameexp, separator, add
;
; on separe widcommand en bloc separes par de + ou des -
; par ex on peut avoir:
; widcommand=2*champ1+champ2-8*champ9+678
;
; si on ne commence pas par un singne + ou -
   case 1 of
      strpos(widcommand, '+') EQ 0:BEGIN
         widcommand = strmid(widcommand, 1)
         firstsign = '+'
      end
      strpos(widcommand, '-') EQ 0:BEGIN
         widcommand = strmid(widcommand, 1)
         firstsign = '-'
      END
      ELSE:firstsign = '+'
   endcase

   sepplus = str_sep(widcommand, '+', /trim)
   sepmoins = str_sep(sepplus[0], '-', /trim)
   singleread = sepmoins
   if n_elements(sepmoins) NE 1 then $
    separator = [replicate('-', n_elements(sepmoins)-1), '+'] ELSE $
    separator = ['+']
   if n_elements(sepplus) GT 1 then $
    for i = 1, n_elements(sepplus)-1 do begin
      sepmoins = str_sep(sepplus[i], '-', /trim)
      singleread = [singleread, sepmoins]
      if n_elements(sepmoins) NE 1 then $
       separator = [separator, replicate('-', n_elements(sepmoins)-1), '+'] ELSE $
       separator = [separator, '+']
   ENDFOR
   separator = [firstsign, separator]
;
   numberofread = n_elements(singleread) 
; cas simple ou il n''y a qu''un champ a lire...
   if numberofread EQ 1 and isnumber(singleread[0]) GE 1 then begin
      coef = ''
      numberofread = 1
      operation = ''
      nameexp = '???'
      separator = ''
      add = separator[0]+singleread[0]
      return
   endif
;
; les dernier element de singleread est-il un ordre de lecture ou une
; constant a ajouter ???
;
   if isnumber(singleread[numberofread-1]) GE 1 then begin
      add = separator[numberofread-1]+singleread[numberofread-1]
      singleread = singleread[0:numberofread-2]
      numberofread = numberofread-1
   ENDIF ELSE add = ''
;
   IF toread GE numberofread then begin
      rien = report('toread ne peut etre + grand que numberofread')
      return
   ENDIF
;
;   for i = 0,  n_elements(singleread)-1 do print, separator[i], ' ',  singleread[i]
;
   pieceofread = singleread[toread]
   separator = separator[toread]
;
   case 1 of
      strpos(pieceofread, '*') NE -1:operation = '*'
      strpos(pieceofread, '/') NE -1:operation = '/'
      ELSE:operation = ''
   ENDCASE
   if operation NE '' then begin
      finalread = str_sep(pieceofread, operation, /trim)
      coef = finalread[0]
      nameexp = finalread[1]
   ENDIF ELSE BEGIN
      if toread EQ 0 AND firstsign EQ '-' then begin
      coef = '-1'
      operation = '*'
      ENDIF ELSE coef = ''
      nameexp = pieceofread
   ENDELSE
;
;
   return
end