Duncan Murdoch wrote:
Romain Francois wrote:
Duncan Murdoch wrote:
Simon Urbanek wrote:
On Jun 18, 2009, at 17:02 , Duncan Murdoch wrote:
Romain Francois wrote:
Hello,
[I'm redirecting this here from stats-rosuda-devel]
When parsing R code through R_parseVector and the code generates
an error (syntax error), is there a way to grab the error.
It looks like yyerror populates the buffer "R_ParseErrorMsg",
but then the variable is not part of the public api.
Would it be possible to add yet another entry point to the
parser that would basically wrap R_parseVector so that it would
have an extra char* argument that would bring back the error
message if there is an error?
I would oppose that. Suggest ways to reduce the complexity of
the parser interface and I'd be interested. It's a nightmare to
make any changes there.
You can always call the R function wrapped in try(), so it's not
as though this would give you anything that you don't already
have access to.
I'm not quite following - we're talking about R_ParseVector in C
code so the point is that the C code gets access to the error
message so it can relay it to the user.
I understood that. But the C code can get the error message by
evaluating an R expression and looking at the result.
There are no R-level functions involved here. The issue here for
the moment is that this information is retrievable at R level but
not (officially) at the C level.
I wouldn't mind exposing the underlying information in a clean way,
but the string in R_ParseVector isn't all a front end should get.
Great. Let's do that.
Is a function that simply returns some of the static variables used
by bison clean enough ?
It could be. I'd like a design that allows for the possibility of
multiple syntax errors to be reported. I have parse_Rd doing that,
though not committed yet. parse() is different because we have to be
less tolerant of errors in R code than in Rd files. But we could
still report multiple errors in one parse, not just stop at the first
one.
This is an interesting problem. Just being curious here: how do you
continue parsing after a syntax error in parse ? Does it depend on the
kind of syntax error ? Do you use some of the recovery protocols of
bison (the special "error" token only appears in the very top level prog
symbol :
prog : END_OF_INPUT { return 0; }
| '\n' { return xxvalue(NULL,2,NULL); }
| expr_or_assign '\n' { return xxvalue($1,3,&@1); }
| expr_or_assign ';' { return xxvalue($1,4,&@1); }
| error { YYABORT; }
;
Anyway, what about using the extra information to structure an error
message of a custom condition class.
Duncan Murdoch
At the time of an R_ParseVector syntax error, the parser knows what
token it couldn't handle, and it knows its classification, and the
location in the file where it came from. Not all of that makes it
through to the error message.
As for reducing complexity - technically, there is no complexity
added since all this is already in place ... [adding extra char *
argument to ParseVector may not be the best way but that's not
what I'm arguing for].
It was what I was arguing against.
Duncan Murdoch
Or am I missing something?
Cheers,
S
Romain
Simon Urbanek wrote:
On Jun 15, 2009, at 12:05 , Romain Francois wrote:
Hello,
In JRI, is there a way to get the error message that is
generated by the
parser through rniParse
For example, if I have this :
long y = re.rniParse( "rnorm( 10 ))", 1 ) ;
this obviously generates a parse error, so y will be the same as
(R_NilValue) :
long null_id = re.rniEval( re.rniParse( "NULL", 1 ), 0 ) ;
I guess the underlying question is : "Is R_ParseErrorMsg
exposed to
JRI".
AFAICT R_ParseErrorMsg and friends are not exposed by the R API
- they are not accessible outside, so they cannot be use by
JRI. It would be nice if there was a way of accessing that
info, but R doesn't currently support that.
Cheers,
Simon
The reason is I would like to bring back the message as part of an
exception generated when the code does not parse.
Romain
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Romain Francois
Independent R Consultant
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http://romainfrancois.blog.free.fr
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