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Anton Antonov Good to know! 14:14
I noticed that after studying Raku for a few years it is much easier to advance my learning of otherprogramming languages. 14:17
I noticed that after studying Raku for a few years it is much easier to advance my learning of other programming languages. 14:43
14:57 frost left
Nemokosch Raku has a very clever built-in collection of data types, for example 16:10
and very nice meta operators
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klebs im seeing a case where a grammar parse ordinarily fails quickly, but then hangs when i try to trace it 19:28
if i kill the trace, i get an output like this:
looks like some kind of infinite loop
but my question is: why would this only be triggered once i add `use Grammar::Tracer;`
no other changes
``` 19:42
#!/usr/bin/env raku 19:43
use my-grammar;
my $in = $*IN.slurp.chomp;
grammar T {
token LIT-CHAR {
\' . \'
}
}
say T.parse("'a'", rule => "LIT-CHAR");
my $parsed = MyGrammar.parse(
$in,
rule => "LIT-CHAR"
);
MyGrammar is, however, a much more substantial grammar with many more rules, but LIT-CHAR is at the leaf position
whoops maybe this shouldn't be in beginner 19:45
(this example is with Grammar::Tracer turned *off*, turning it on *hangs* on the second parse)
```
#!/usr/bin/env raku
use my-grammar;
my $in = $*IN.slurp.chomp;
grammar T {
token LIT-CHAR {
\' . \'
}
}
say T.parse("'a'", rule => "LIT-CHAR");
MasterDuke i think it's known that Grammar::Tracer can sometimes interfere with what it's tracing 19:47
klebs (this example is with Grammar::Tracer turned *off*, turning it on *hangs* on the second parse)
```
#!/usr/bin/env raku
use my-grammar;
my $in = "'a'";
grammar T {
token LIT-CHAR {
\' . \'
}
}
say T.parse($in, rule => "LIT-CHAR");
my $parsed = MyGrammar.parse(
MasterDuke i don't know if there's any workaround though
klebs debugging the debugger 🙂 19:48
that may explain the hang, however why do we get a `failed match`? 19:49
(when running without Grammar::Tracer)
seems to me like it should succeed because it is the same rule at toplevel
MasterDuke you're saying you get `｢'a'｣` but then it fails the second time? 19:53
klebs yes 19:57
one other detail perhaps of note is that this grammar is created by mixing in about 130 different roles 19:59
so it is pretty big
meant to parse a full language
but i dont see why that should cause a failed match when i directly specify the rule via the parse method as shown above
MasterDuke i haven't actually done much with grammars so not sure i can be any more use, but if guifa or codesections can't help you here, i'd recommend asking moritz over in #raku 20:03
klebs thanks for the help 🙏 20:05
MasterDuke np 20:07
klebs i found a way to drill down and locate the source of the problem 20:56
basically just binary search commenting and uncommenting batches of tokens 20:57
will find it soon
i think there might be some other rule the grammar engine doesn't like
which is causing faulty behavior
that is my best gues
that is my best guess
yep that was the problem 20:59
for some reason this was an error:
`token MATCH { match }`
changing to `token MATCH_ { match }`
solved
gfldex @klebs#2209 I believe you stepped onto: github.com/Raku/nqp/blob/master/sr....nqp#L1101 21:04
MasterDuke ah yes, using names already used in the core can cause odd problems
gfldex or github.com/rakudo/rakudo/blob/mast...ch.pm6#L40 21:05

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