| Time |
Nick |
Message |
| 00:00 |
jeffreykegler |
pczarn -- you might want to get into reading papers on parsing -- even when you can reinvent a field, it is much better to understand the traditions and conventions that preceded you. |
| 00:02 |
djns |
hi |
| 00:03 |
djns |
Can Marpa parse an "unrestricted grammar" and a "context sensitive grammar" |
| 00:11 |
|
jeffreykegler joined #marpa |
| 00:11 |
jeffreykegler |
djns: No. |
| 00:14 |
djns |
Are they just too difficult to parse |
| 00:14 |
djns |
Would it be hard to write such a parser |
| 00:14 |
jeffreykegler |
That's an open question. |
| 00:15 |
jeffreykegler |
A few years ago, folks said general context free (CFG) parsing was too hard for practical use. |
| 00:15 |
jeffreykegler |
A lot of folks are still saying that, in fact. |
| 00:16 |
jeffreykegler |
Perhaps somebody on this channel will be the one to solve the CSG problem. |
| 00:23 |
djns |
maybe so |
| 01:00 |
|
jeffreykegler joined #marpa |
| 02:33 |
|
ceridwen joined #marpa |
| 03:14 |
ronsavage |
Re CSGs: One of my modules, https://metacpan.org/release/GraphViz2-Marpa, switches between grammars during a single pass of the input :-). Does that count? |
| 03:18 |
jeffreykegler |
Depends who is counting :-) |
| 03:19 |
jeffreykegler |
I know some people in describing PEG's tendency to do wierd things with your BNF specification would call this the ability to parse CSG's ... |
| 03:19 |
jeffreykegler |
but to my mind it was like taking selling a used car with bad suspension and tricky steering by describing it as an off-road vehicle |
| 03:56 |
djns |
My understanding is that the Left Hand Side contains a sequence of rules to be replaced by the right hand side, in the BNF code of the parser itself,when using a CSG? So, the BNF code modifies itself? |
| 03:57 |
djns |
In other word, the code already defined previously in the set of rules that matches the left hand side is replaced by the right hand side |
| 03:57 |
jeffreykegler |
No, the BNF is not self-modifying. |
| 03:58 |
jeffreykegler |
It remains static and a string of symbols is repeatedly rewritten according to the BNF rules |
| 03:58 |
djns |
i see |
| 05:57 |
|
ronsavage joined #marpa |
| 07:32 |
ronsavage |
jk: Re http://irclog.perlgeek.de/marpa/2015-07-30#i_10975648. Well, if no-one else is counting, I'll count for myself........ |
| 07:48 |
|
pczarn joined #marpa |
| 08:40 |
|
purmou joined #marpa |
| 09:16 |
pczarn |
that's right, until now I've been reading papers only to learn details, not conventions |
| 09:19 |
pczarn |
parsing is different |
| 09:22 |
pczarn |
My rewrite of libmarpa started a little late |
| 09:24 |
pczarn |
there are a few parser combinator libraries and even a LALR parser in Rust |
| 09:41 |
pczarn |
and this rewrite is moving along so slowly I might as well stop writing for now |
| 12:43 |
|
koo7 joined #marpa |
| 13:00 |
|
pczarn joined #marpa |
| 13:05 |
djns |
hi |
| 13:19 |
pczarn |
hi |
| 16:11 |
|
idiosyncrat joined #marpa |
| 16:16 |
idiosyncrat |
rns, ronsavage: Do you think MarpaX::Languages::Lua::Parser is ready to announce on the Lua mailing list? |
| 17:22 |
|
pczarn joined #marpa |
| 17:54 |
|
lwa joined #marpa |
| 17:59 |
mvuets |
hi! |
| 18:15 |
|
idiosyncrat joined #marpa |
| 18:16 |
idiosyncrat |
This article "Have a theory" from Aria's twitter feed -- http://whilefalse.blogspot.com/2015/07/have-theory.html |
| 18:16 |
idiosyncrat |
I mention it here because I think it's very important in programming. |
| 18:17 |
idiosyncrat |
Always know *why* you think what you are doing will work ... |
| 18:17 |
idiosyncrat |
or if it is an experiment, what it is that you are testing. |
| 18:18 |
Aria |
Yes! |
| 18:18 |
idiosyncrat |
The theory need not be right -- there's no way of guaranteeing that. |
| 18:18 |
idiosyncrat |
But with no theory you may not realize you are wrong, and if you are wrong you certainly won't know in what way you are wrong. |
| 18:19 |
idiosyncrat |
Have a theory -- do *not* just hack. |
| 18:21 |
idiosyncrat |
Einstein (with his assistant Infeld) wrote a combined history of physics and scientific autobiography ... |
| 18:21 |
idiosyncrat |
called _The Evolution of Physics_, and it repeatedly makes this point. |
| 18:22 |
idiosyncrat |
Theory (for Einstein) is far more important than experiment ... |
| 18:23 |
idiosyncrat |
without a theory the experiment may not get carried out and, in any case, won't be able to be interpreted. |
| 18:24 |
|
rns joined #marpa |
| 18:24 |
idiosyncrat |
It's an important book, much neglected, I suspect because it's message is so different from the current outlook. |
| 18:41 |
rns |
idiosyncrat: re http://irclog.perlgeek.de/marpa/2015-07-30#i_10978829 -- can't really say no, but AFAIK, currently it can hardly offer something the Lua community doesn't already have. |
| 18:54 |
idiosyncrat |
rns: You can always say no :-) |
| 18:55 |
idiosyncrat |
It would alert them to our interest in Lua, and may draw their interest to Marpa. |
| 18:55 |
idiosyncrat |
Also, I don't think they really have a good "luatidy", and the best one is, in fact, in Perl. |
| 18:56 |
idiosyncrat |
So |
| 18:56 |
idiosyncrat |
MarpaX::Languages::Lua::Parser may in fact fill a real need. |
| 19:01 |
|
koo7 joined #marpa |
| 19:01 |
rns |
Well, from what I've been reading on lua-l, they can benefit from what I'd call luafmt/luafix, a-la gofmt/gofix of Go lang -- luafmt to ensure consistent formatting/style (though they are not much into that, IFAIK, more into checking, e.g. luacheck) and luafix to apply AST-transform-based compatibility fixes between 5.1, 5.2, and 5.3. |
| 19:02 |
rns |
So smth. like luatidy is an opportunity, yes. |
| 19:04 |
rns |
idiosyncrat: BTW, perhaps you can take a look at https://github.com/ronsavage/MarpaX-Languages-Lua-Parser/issues/2 if/when you have time -- the example is from Lua 5.1 test suite. |
| 19:04 |
mvuets |
after my Monday talk someone came to me and asked where did i manage to find proper documenation for Marpa |
| 19:05 |
mvuets |
in fact documentation did seem complex to me at first too. but after constantly approaching it multiple times i realized it's actually very good |
| 19:05 |
mvuets |
comprehensive and well written |
| 19:06 |
idiosyncrat |
mvuets: Thank you |
| 19:06 |
idiosyncrat |
The documentation is intended to be "expert-friendly" first, newcomer-friendly second. |
| 19:07 |
idiosyncrat |
So if I have a choice between stating something exactly, vs. less formally, but more clear. |
| 19:07 |
idiosyncrat |
I go the first way. |
| 19:08 |
idiosyncrat |
These days I don't have time to do both, and my thinking is that my first priority is to make it possible for somebody who's already well-informed to understand Marpa. |
| 19:08 |
idiosyncrat |
Hopefully, he will go out and give talks, etc., and help the others. :-) |
| 19:09 |
idiosyncrat |
A lot of Perl docs just give a rough idea of what's going on, and leave it to the user to find out the details by experiment, etc. |
| 19:10 |
idiosyncrat |
That may work OK for other applications, but my feeling with a tool like Marpa, you need a *precise* and full specification ... |
| 19:10 |
idiosyncrat |
even if that means it is not an easy read. |
| 19:14 |
idiosyncrat |
rns: re http://irclog.perlgeek.de/marpa/2015-07-30#i_10979866 -- Thanks. I'll take a peek |
| 19:29 |
mvuets |
re docs: on the other hand, the calculator example is a bit boring (-: |
| 19:30 |
idiosyncrat |
mveuts: you might say it was chosen for that reason. |
| 19:30 |
idiosyncrat |
It *is* familiar, and in doing Marpa docs, I'm desperate for anything that roots what I am saying in things the reader already knows. |
| 19:31 |
idiosyncrat |
rns: Yes, change the precedence to match Lua's behavior, even if that conflicts with its reference manual. |
| 19:40 |
idiosyncrat |
rns: Actually, on experiment, Lua's behavior is strange. I've added a comment to the issue. |
| 19:47 |
rns |
FWIW, lua's exponentiation precedence is really higher than unary minus -- lua -e 'print(-2^2)' says -4 and so does perl -M5.010 -e 'say -2**2', BTW. |
| 19:49 |
rns |
Problem is, MarpaX-Languages-Lua-Parser parses 2^-2, but fails at chained unary minuses - -2 — in -2^- -2. |
| 19:57 |
rns |
chained unary minuses in the exponent, that is. |
| 20:14 |
|
idiosyncrat joined #marpa |
| 20:16 |
idiosyncrat |
Actually, the precedence seems to be a difference in the RHS of an exponentiation ('^') from its LHS |
| 20:17 |
idiosyncrat |
The most elegant solution might be to make an exponent special kind of expression ... |
| 20:17 |
idiosyncrat |
on which has its own (much smaller) precedenced statements |
| 20:18 |
idiosyncrat |
Here is something we'd bring to Lua that will truly *add value* -- for the first time, there will be a proper BNF grammar of Lua ... |
| 20:18 |
idiosyncrat |
and not only that that, but it will come in a form that allows them to check it ... |
| 20:18 |
idiosyncrat |
and even experiment with revisions and extensions. |
| 20:29 |
idiosyncrat |
Have to run errands -- AFK |
| 22:57 |
|
ronsavage joined #marpa |
| 22:57 |
ronsavage |
jk: Re http://irclog.perlgeek.de/marpa/2015-07-30#i_10978829. Yes, it's on CPAN, and ready to be used. And I can (presumably!) fix any issues which arise. |
