[ckok]

Parser generators generally suffer from at least speed, recovery, error handling and lack of debuggability. They also require you to learn a new language, the parser generators language.

Last but not least, what you actually end up wanting to build is an ast, as at some point you want to do something with the input, for most parsers you then have to implement even more code to build up the ast.

It is much easier to hand write it. In the end its faster to write and usually faster to run.

Every few years I evaluate the new options for the languages I use (c#, pascal), every time so far I am disappointed with the tooling. Maybe one year.

[Zababa]

I think you have to see them a bit like regexes. It may be a bit annoying to learn the grammar at first, but it's cross-language learning in a way, as you can use parser generators libraries in any language.

[chrisseaton]

But it's still one extra language to learn, for in practice no benefit.

[Zababa]

Copy/pasting the grammar of a language and using a library will be faster to do than any hand-written implementation, so I don't agree that there are no benefits.

[chrisseaton]

But you can't do that because in practice these grammars have lots of imperative action code inserted all over the place because the parser generator's model fundamentally doesn't match the language class you're parsing and it needs to be worked around.

For example I work with a parser definition that's supposedly shared between C and Java, but it's a massive nightmare because it's 50% imperative actions.

[Zababa]

That depends on the language you're trying to parse. If it has a LL or LR grammar, it'll work well. If it's something else that can't be described with something like that or something less powerful, you're going to have a bad time.

[chrisseaton]

> That depends on the language you're trying to parse.

Yes... but most practical languages do not have simple LL or LR grammars. Hence this blog post and discussion and these problems.