Dimension error with `r_vector`
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Assessment
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Newbie friendliness
- 35/100
Research direction
Start by reproducing the supplied cpp_function example and inspect how r_vector handles R_DimSymbol and validates dimensions. The issue is done when a six-element vector can accept dimensions {2, 3} without reporting length 8, with a regression test covering the example.
Written by the indexing model from the issue text.
Description
Hi, thanks for this wonderful package. As I was playing around with the r_vector class, I found the following peculiar behavior and I think this might be a bug. Specifically, there should only be 6 elements, but when writing the dimensions to the vector, it returns an error saying there's 8 elements.
cpp11::cpp_function(
"
SEXP test() {
using namespace cpp11;
writable::r_vector<double> vec; // Start empty
// Dynamically add data
vec.push_back(1.0);
vec.push_back(2.0);
vec.push_back(3.0);
vec.push_back(4.0);
vec.push_back(5.0);
vec.push_back(6.0);
message(\"size: %i\", vec.size());
// Now decide dimensions (2 rows by 3 columns)
vec.attr(R_DimSymbol) = writable::r_vector<int>({2, 3});
// Create matrix from the vector
// writable::doubles_matrix<> mat(vec.data());
return(vec.attr(R_DimSymbol));
}
"
)
test()
#> size: 6
#> Error in test(): dims [product 6] do not match the length of object [8]
Created on 2025-07-21 with reprex v2.1.1
Disclaimer: This example was taken from some code snippets from Claude while I was trying to understand the internals of this package.
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- C++
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