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https://github.com/masterodin/cfg2cnf
A Context-Free Grammar to Chomsky Normal Form Parser
https://github.com/masterodin/cfg2cnf
Last synced: 27 days ago
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A Context-Free Grammar to Chomsky Normal Form Parser
- Host: GitHub
- URL: https://github.com/masterodin/cfg2cnf
- Owner: MasterOdin
- License: mit
- Created: 2014-11-06T04:49:36.000Z (about 10 years ago)
- Default Branch: master
- Last Pushed: 2014-11-06T21:16:08.000Z (about 10 years ago)
- Last Synced: 2024-05-01T12:16:19.362Z (6 months ago)
- Language: PHP
- Homepage:
- Size: 133 KB
- Stars: 7
- Watchers: 3
- Forks: 3
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
CFG2CNF
=======
A Context-Free Grammar to Chomsky Normal Form
[Chomsky Normal Form](http://en.wikipedia.org/wiki/Chomsky_normal_form) is a context-free grammar that has been put into a specific format. It was developed by Noam Chomsky in 1978 and is part of formal language theory.
It performs the the steps listed [here](http://en.wikipedia.org/wiki/Chomsky_normal_form#Converting_a_grammar_to_Chomsky_Normal_Form) to convert from the one grammar to the other.
Known Inputs
------
Known inputs that work and what their outputs should be:
(Textbook used was Michael Sipser's Theory of Computation 3rd Edition)
--
Example of how to convert, shown on pg. 108 of textbook
```
S -> ASA | aB
A -> S | B
B -> b | /
```
gives (copied from book):
```
S0 -> AC | UB | a | SA | AS
S -> AC | UB | a | SA | AS
A -> b | AC | UB | a | SA | AS
C -> SA
U -> a
B -> b
```
Program gives:
```
S0 -> AC | DB | a | SA | AS
S -> AC | DB | a | SA | AS
A -> AC | DB | a | SA | AS | b
B -> b
C -> SA
D -> a
```
where D corresponds to U, and that is the only difference
--
Exercise 2.14 (page 129):
```
A -> BAB | B | /
B -> 00 | /
```
gives: (solved by University of Central Florida and displayed in a PDF of selected solutions: http://www.cs.ucf.edu/courses/cot4210/fall04/answers/hw4sol.pdf)
```
S0 -> BA1 | AB | BA | B1 B1 | BB | /
A -> BA1 | AB | BA | B1 B1 | BB
B -> B1B1
B1 -> 0
A1 -> AB
```
Execution of program gives:
```
S0 -> BC | AB | BA | BB | DD | /
A -> BC | AB | BA | BB | DD
B -> DD
C -> AB
D -> 0
```
D corresponds to B1, A1 to C.
Note: outputs from the program may not match perfectly with non-terminals used, but rules match, which is important part.