Results

**1 - 3**of**3**### 1 Pushdown Automata ⋆

"... Recursive functions in a computer program can be modelled by suitable grammatical rules. As an example, cf. Figure 1.1, the recursive function Hanoi, moving n disks from pin s to pin t using additional pin v can be represented by productions like Hstv(n) → Hsvt(n−1) mst Hvts(n−1) and Hstv(0) → λ ..."

Abstract
- Add to MetaCart

Recursive functions in a computer program can be modelled by suitable grammatical rules. As an example, cf. Figure 1.1, the recursive function Hanoi, moving n disks from pin s to pin t using additional pin v can be represented by productions like Hstv(n) → Hsvt(n−1) mst Hvts(n−1) and Hstv(0) → λ

### Flip-pushdown automata: nondeterministic ε-moves can be removed ⋆

"... Abstract. Flip-pushdown automaton is pushdown automaton which has ability to flip its pushdown throughout the computation. This model was introduced in [3] by Sarkar. Here we solve in the affirmative the following open problem posed by Holzer and Kutrib in [1]: What is the power of ε-moves for nonde ..."

Abstract
- Add to MetaCart

Abstract. Flip-pushdown automaton is pushdown automaton which has ability to flip its pushdown throughout the computation. This model was introduced in [3] by Sarkar. Here we solve in the affirmative the following open problem posed by Holzer and Kutrib in [1]: What is the power of ε-moves for nondeterministic flip-pushdown automata – can they be removed without affecting the computational capacity? (ε denotes the empty word.) Moreover, we prove here that the family of languages recognized by the deterministic variant of the flip-pushdown automata (with k-pushdown reversals) is closed under intersection with regular sets, complement and inverse homomorphism, but it is not closed under union, intersection, (non-erasing) homomorphism, reverse, concatenation and (positive) iteration. Finally, we formulate some new questions and pose new problems. 1