FUNCTION where_is_in, ARR1, ARR2, OTHER=other
; gives back indeces of ARR1 where its contents equal one of the
; enties in ARR2
   iuni = UNIQ(ARR2)
   tind = where(ARR1 EQ ARR2[iuni[0]])
   nl = N_ELEMENTS(ARR2)
   IF (nl GT 1) THEN BEGIN
      FOR i=1,nl-1 DO BEGIN
         ind = where(ARR1 EQ ARR2[iuni[i]])
         tind = [tind, ind]
      ENDFOR
   ENDIF
   
   RETURN, tind
END