Hi, the code below presents an unexpected behaviour to me. I declare an array of 10 2x2 matrix called “S”. If I print the first element S[1] everything seems fine. If I sum S[1] to a 3x3 matrix “R” now S[1] becomes ifself a 3x3 matrix.

My question is, shouldn’t Stan raise an error during the summarion between different sized matrices (but I suppose that the answer lies in the way that array of matrices is stored in the memory)? And also, why printing before and after the summation display a change in matrix size for S[1]?

thank you

```
data {}
parameters {}
transformed parameters{
matrix[2,2] S[10];
matrix[3,3] R = [[1,2,3], [4,5,6], [7,8,9]];
// here S[1] is a 2x2 matrix
print("S[1] before summation");
print(S[1]);
// Why is this allowed? S[1] is 2x2 while R is 3x3
S[1] = R;
// now S[1] is a 3x3 matrix
print("S[1] after summation");
print(S[1]);
}
model {
}
```