Hi,
I am not going to work out why you code crashes, but I did manage to
bypass dim checking some time ago - and as others had replied, it is
Not a Good Idea (TM) , as the check is there for a reason. If you really
want to do it, here is the relevant snipplet of what I did (oh, I did
copy installAttrib() from R/src/main/attrib.c - it is declared static
there so you can cut-and-paste the whole routine to your code) - but
as others had said, it is Not a Good Idea:
...
SEXP ans, dim, dimnames, class;
...
PROTECT(dim = allocVector(INTSXP, 2));
...
INTEGER(dim)[0] = i;
INTEGER(dim)[1] = j;
...
PROTECT(dimnames = allocVector(VECSXP, 2));
SET_VECTOR_ELT(dimnames, 0, R_NilValue);
SET_VECTOR_ELT(dimnames, 1, R_NilValue);
...
/* we bypassed the checks for Dimname and Dim */
installAttrib(ans, R_DimNamesSymbol, dimnames);
installAttrib(ans, R_DimSymbol, dim);
...
return ans;
...
Hin-Tak Leung
miguel manese wrote:
> Hello,
>
> I created an S3 "type" w/c is actually a list that should look like a
> matrix but whose data is actually in an external file. The SEXP just
> contains info on how to retrieve the data from the file. When I get to
> the part of creating the SEXP, I found out that SET_DIM & SET_DIMNAME
> checks the SEXP if the length matches (somewhere in src/main/attrib.c,
> dimgets & dimnamegets IIRC (it's on my other partition. life sucks)).
> After a quick look at the R code, I tried to bypass them by doing:
>
> static void _installAttrib(SEXP obj, SEXP name, SEXP value) {
> /* to bypass dim & dimnames property checking */
> SEXP attr, cur_attr;
> PROTECT(attr = NEW_LIST(1));
> SETCAR(attr, value);
> SET_TAG(attr, name);
> if (ATTRIB(obj) == R_NilValue) SET_ATTRIB(obj, attr);
> else {
> cur_attr = nthcdr(ATTRIB(obj), length(ATTRIB(obj)) - 1);
> SETCDR(cur_attr, attr);
> }
> UNPROTECT(1);
> }
>
> but it crashes R. Is there any other way to do this other than copying
> those code in R that was not included in the API ?
>
> Thanks,
> M. Manese
>
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