Dear Listmembers, wanting to learn more about ALTREP I wrote the following function to extract a subsequence from an integer vector:
#include <Rinternals.h>
SEXP integer_get_region(SEXP _x, SEXP _i, SEXP _n) {
int i = INTEGER(_i)[0];
int n = INTEGER(_n)[0];
SEXP result = PROTECT(Rf_allocVector(INTSXP, n));
INTEGER_GET_REGION(_x, i, n, INTEGER(result));
UNPROTECT(1);
return result;
}
For "shorter" vectors, the result is as expected:
> dyn.load("altrep_int_region.so")
> .Call("integer_get_region", 1:1e9, 0L, 10L)
[1] 1 2 3 4 5 6 7 8 9 10
But not for "longer" vectors:
> .Call("integer_get_region", 1:1e10, 0L, 10L)
[1] 0 1072693248 0 1073741824 0 1074266112
[7] 0 1074790400 0 1075052544
Am I doing something wrong or is this a bug? I am using
> R.version.string
[1] "R version 3.5.2 (2018-12-20)"
Thanks
Ralf
--
Ralf Stubner
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