In formal language theory, a leftist grammar is a formal grammar on which certain restrictions are made on the left and right sides of the grammar's productions. Only two types of productions are allowed, namely those of the form [math]\displaystyle{ a \to ba }[/math] (insertion rules) and [math]\displaystyle{ cd \to d }[/math] (deletion rules). Here, [math]\displaystyle{ a,b,c }[/math] and [math]\displaystyle{ d }[/math] are terminal symbols. This type of grammar was motivated by accessibility problems in the field computer security.[1]
Computational properties
The membership problem for leftist grammars is decidable.[1]
See also
- Unrestricted grammar
- String rewriting
Automata theory: formal languages and formal grammars |
|---|
| Chomsky hierarchy | Grammars | Languages | Abstract machines |
- Type-0
- —
- Type-1
- —
- —
- —
- —
- —
- Type-2
- —
- —
- Type-3
- —
- —
|
- Unrestricted
- (no common name)
- Context-sensitive
- Positive range concatenation
- Indexed
- —
- Linear context-free rewriting systems
- Tree-adjoining
- Context-free
- Deterministic context-free
- Visibly pushdown
- Regular
- —
- Non-recursive
|
- Recursively enumerable
- Decidable
- Context-sensitive
- Positive range concatenation*
- Indexed*
- —
- Linear context-free rewriting language
- Tree-adjoining
- Context-free
- Deterministic context-free
- Visibly pushdown
- Regular
- Star-free
- Finite
|
- Turing machine
- Decider
- Linear-bounded
- PTIME Turing Machine
- Nested stack
- Thread automaton
- restricted Tree stack automaton
- Embedded pushdown
- Nondeterministic pushdown
- Deterministic pushdown
- Visibly pushdown
- Finite
- Counter-free (with aperiodic finite monoid)
- Acyclic finite
|
|
Each category of languages, except those marked by a *, is a proper subset of the category directly above it. Any language in each category is generated by a grammar and by an automaton in the category in the same line. |
References
- ↑ 1.0 1.1 Motwani, Rajeev; Panigrahy, Rina; Saraswat, Vijay; Ventkatasubramanian, Suresh (2000). "Proceedings of the thirty-second annual ACM symposium on Theory of computing - STOC '00". Proceedings of the thirty-second annual ACM symposium on Theory of computing (STOC '00). pp. 306–315. doi:10.1145/335305.335341. ISBN 1581131844.
 | Original source: https://en.wikipedia.org/wiki/Leftist grammar. Read more |