Test if a sentence can be generated by given BNFs (Backus-Naur-Form).
Based on some very simple generation rule in BNF it should be possible to decide whether a sentence could be generated or not.
The program expects 2 different
- BNF-Definitions, starting with
#def name(multiple BNFs allowed, see example) - and tests, starting with
#tests(only one section allowed). On each following line, the program expects a name for the test case and the test case itself, separated by a space (the test case itself mustn't contain spaces).
BNF definitions should follow the following syntax:
a := a | "b" a | a "c" a | ...
where quoted terms mean Terminals and the recursively defined word a is a Nonterminal. This "production rule" simply means that a can be expanded to one of the following terms. The different possibilities are separated by |.
Currently it is not possible to work with more than one Nonterminal (as the exercise in the course only stated the simple BNFs from below :).
For two given BNFs and some examples as from the HCI-book, they can be written as stated,
#def bnf1
sentence := _ | "hello" sentence | "(" sentence ")" sentence
#def bnf2
sentence := "hello" | sentence sentence | "(" sentence | sentence ")"
#tests
(a) hello
(b) hello(hello)
(c) ((hello)
(d) ()
...
Where _ is a metavariable with the meaning (empty). All spaces or quote signs will be ignored.
This should yield the following result:
Definition found: bnf1
Definition found: bnf2
Building rules...
Cleaning rules...
rules: [['x', '', 'hellox', '(x)x'], ['x', 'hello', 'xx', '(x', 'x)']]
Running tests...
Test (a) hello <-- bnf1 bnf2
Test (b) hello(hello) <-- bnf1 bnf2
Test (c) ((hello) <-- bnf2
Test (d) () <-- bnf1
Test (e) (hello)hello <-- bnf1 bnf2
Test (f) ((hello))hello <-- bnf1 bnf2
Test (g) hello()hello <-- bnf1
Test (h) (hellohello) <-- bnf1 bnf2
Test (i) )hello( <--
Test (j) hello)(hello <-- bnf2
Test (k) hello() <-- bnf1
Test (l) (hello)hello(hello) <-- bnf1 bnf2
Test (m) (hello((hello)hello <-- bnf2
Test (n) (((hello)))) <-- bnf2
Test (o) ((((hello)))) <-- bnf1 bnf2
Test (p) ((((hello()))) <--
Test (q) (((hello()))) <-- bnf1
Example (n) here is only a valid production in bnf2, but not in bnf1. (a) is valid in both and (i) is valid in neither of them.
No warranty for use. The code was written for validating sentences in the course Human-Computer-Interaction.