Re: [tlug] presentation wish list

[Noda Yoshikazu <noda.yoshikazu@example.com>]

> However, I am not sure whether it is desirable when out of a total of
> six technical meetings per year, three of them are about parsing.
> There will be folks who are not all that interested in parsing.

I could hardly imagine  people would be interested in parsing (context
free) languages.
Actually writing parsers using the tools like flex & bison is VERY old
school thing to do,
as it's a 50 year old technology. Nowadays I always opt for using
ANTLR as it makes
the task much easier.

That said, IMHO the knowledge is language parsing is something good to
have for all
programmers.

2014-10-13 20:44 GMT+09:00 Benjamin Kowarsch <trijezdci@example.com>:
> On 13 October 2014 13:04, Travis Cardwell
> <travis.cardwell@example.com> wrote:
>>
>> These days, I prefer PEG/packrat over LL(n)
>
> For the sake of correctness, ANTLR uses what Terence Parr dubbed LL(*)
> which is LL(n) for arbitrary values of n. This uses memoisation to
> avoid costly backtracking and for all practical purposes it is
> functionally equivalent to PEG.
>
> However, for a discussion of RD parsing it is best to introduce the
> concept on the basis of LL(1) then expand from that towards values of
> n > 1 and show how this impacts the parsing algorithm and its
> complexity as it requires techniques such as memoisation or
> backtracking.
>
> There are other techniques that can enhance LL grammars in ways that
> would otherwise require more complex grammars such as LR and GLR. For
> example, we wanted to use one symbol both as a reserved word and as an
> identifier depending on context. Usually this would require a much
> more complex grammar but we found a paper for a technique called
> "Schroedinger's Token" which allows the decision whether a given token
> is one of two (or more) things from the lexer to the parser where the
> parser usually has the context information to resolve the ambiguity.
> This can be implemented with astonishingly little effort.
>
>>
>>> Anyway, I could give a presentation that covers:
>>>
>>> (1) the concept of recursive descent parsing
>>> (2) how to craft an LL(n) grammar that can be parsed using RD
>>> (3) how to translate an LL(n) grammar directly into code
>>> (4) how to use ANTLR to visualise and verify a grammar and visualise conflicts
>>> (5) summarise the benefits of LL parsing in general and ANTLR as a
>>> prototyping tool
>>>
>>> However, parsing is a fairly complex subject matter. I doubt that it
>>> would be a good idea to cover a presentation for LR parsing and
>>> flex/bison as well as LL parsing and RD/ANTLR on a single day. It is
>>> probably better to do this on two separate meetings.
>>
>> That does indeed sound like it would be a bit much for one meeting!
>
> Indeed. Thus if there is somebody who likes to do a session on LR
> parsing and flex/bison, that would be sufficient material for one
> meeting. A presentation covering LL parsing, RD and ANTLR would be
> material for another.
>
> Should there be interest and a presenter to go even further, a
> presentation covering PEG and packrat would expand on the LL RD/ANTLR
> presentation and be material enough for a third meeting.
>
> However, I am not sure whether it is desirable when out of a total of
> six technical meetings per year, three of them are about parsing.
> There will be folks who are not all that interested in parsing.
>
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