/* create an interpolation using a1 and a2, (defaulting to previous and next) */
/* if not possible, just fill from a1 (or from template if given) and return 0 */
virtual int interpolate_from(Auto *a1, Auto *a2, int64_t new_position, Auto *templ=0);
/* create an interpolation using a1 and a2, (defaulting to previous and next) */
/* if not possible, just fill from a1 (or from template if given) and return 0 */
virtual int interpolate_from(Auto *a1, Auto *a2, int64_t new_position, Auto *templ=0);