Abstract
In a previous paper Rozenberg (1974) introduced the PDAC acceptors (pushdown-array-of-counters acceptors) and showed that the restricted PDACA characterize the EOL languages. In this present note the PDAPDA (pushdown-array-of-pushdowns acceptors) are introduced and it is shown that the restricted PDA2 characterize the ETOL languages.
† The work of the second author was partially supported by a National Research Council of Canada Grant No. A-7700 and partially under the auspices of the Mathematical Institute of Utrecht University.
† The work of the second author was partially supported by a National Research Council of Canada Grant No. A-7700 and partially under the auspices of the Mathematical Institute of Utrecht University.
Notes
† The work of the second author was partially supported by a National Research Council of Canada Grant No. A-7700 and partially under the auspices of the Mathematical Institute of Utrecht University.