Grammer Tester

[Moondee]

Is it possible that given a PEG grammar, generate a random string that satisfies the given grammar and then test this string?

[PhilippeSigaud]

Pegged cannot produce the language a grammar defines, if that is what you
mean.

[Moondee]

What I meant was suppose we have a grammar for a calculator.
Can Pegged generate valid sequences for the calculator grammar? like randomly generate ' 1+2'...

[PhilippeSigaud]

What I meant was suppose we have a grammar for a calculator.
Can Pegged generate valid sequences for the calculator grammar? like
randomly generate ' 1+2'...

No, it cannot.

Hmm, I don't know of a parser generator doing that, even though grammars
are supposed to be generative in nature (that is, used to produce
sentences, not to parse them).

You know, even for small languages, I don't think that would be that
interesting: most of the generated strings would be useless ("1", "2",
"11", ..., not even reaching a '+' part), unless it iterates the grammar in
a breadth-first way. And that's not even taking white spaces into account.
'Most' of the sentences thus generated would be far too simple to be of any
use, in case you were thinking about generating programs from a programming
language grammar.

[Moondee]

Thanks. I agree. Surprisingly I see several string generators for CFG like Yagg , DGL,..., though have't seen any for PEG based language.

[PhilippeSigaud]

Thanks. I agree. Surprisingly I see several string generators for CFG like
Yagg , DGL,..., though have't seen any for PEG based language.

Do you know what people use them for? To verify the grammar they wrote
indeed generates the right language?