glr support in goyacc?

[David Wahlstedt]

Hi,

I wonder if there are any plans to add the "glr" option to goyacc (it doesn't look as if this is the case) ?

According to this thread,

https://stackoverflow.com/questions/25976394/how-to-resolve-ambiguity-in-the-definition-of-an-lr1-grammar

golang is "not LALR(1), nor LR(k) for any k".

So, if golang has been bootstrapped, compiled with itself, how did they write the parser?

By hand, or by using an LR parser and tweaking the grammar?

Then, shouldn't be a good idea for goyacc to have "glr" support, as there is in e.g. bison?

Sorry if my question is naive (it is, probably), I am new to golang.

BR,

David

[Jan Mercl]

On Thu, Mar 8, 2018 at 7:44 PM David Wahlstedt <david.wah...@gmail.com> wrote:

> So, if golang has been bootstrapped, compiled with itself, how did they write the parser?
> By hand, or by using an LR parser and tweaking the grammar?

Go authors initially used a modified grammar (distilled version at https://github.com/cznic/gc/blob/b007e32c610fc39d850653c9b09d7515507f2b6e/testdata/parser/parser.y) in combination with a simple transformation of the input token stream in the lexer (functionally equivalent Go implementation can be seen also at https://github.com/cznic/gc/blob/b007e32c610fc39d850653c9b09d7515507f2b6e/all_test.go#L976).

Nowadays the gc uses a handwritten parser, so the class of the language no more matters [that much]. (Alternative experimental implementation also at https://github.com/cznic/gc/blob/b007e32c610fc39d850653c9b09d7515507f2b6e/parser.go)

IMHO, GLR would be an overkill for a Go parser.

--

-j

[David Wahlstedt]

Ok, I see!

But it would still be nice to have GLR in goyacc, for instance in order to write an ASN.1 parser.

[Ian Lance Taylor]

On Fri, Mar 9, 2018 at 12:27 AM, David Wahlstedt
<david.wah...@gmail.com> wrote:
>
> But it would still be nice to have GLR in goyacc, for instance in order to
> write an ASN.1 parser.

I'm not aware of anybody working on that.

Ian

[David Wahlstedt]

There are people working on it. This for instance:

https://github.com/chemikadze/asn1go

Furthermore, if you want to write telecom applications in go(where ASN.1 is common), it is quite natural to want an ASN.1 parser.

BR,

David

[Matt Harden]

I believe Ian was saying he's not aware of anybody working on adding GLR support to goyacc.

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