Re: Why can't I pass a const array to a function that takes scope const arrays?

[Paul Backus via Digitalmars-d-learn]

On Monday, 17 February 2020 at 20:08:24 UTC, Adnan wrote:
On Monday, 17 February 2020 at 14:34:44 UTC, Simen Kjærås wrote:
On Monday, 17 February 2020 at 14:04:34 UTC, Adnan wrote:
//

All in all, I end up with this code:

module strassens_matmul
package {
    T[][] mulIterative(T)(const T[][] mat1, const T[][] mat2) {
        auto result = createMatrix!T(getRowSize!T(mat1), 
getColumnSize!T(mat2));
        foreach (row; 0 .. mat1.getRowSize()) {
            foreach (column; 0 .. mat2.getColumnSize()) {
                T value;
                foreach (i; 0 .. mat1.getRowSize()) {
                    value += mat1.getPointCopy(row, i) * 
mat2.getPointCopy(i, column);
                }
                *result.getPointPtr(row, column) = value;
            }
        }
        return result;
    }
}

Aren’t these passing by values? That’s why I used ref. Plus 
since I don’t want to change the arrays in the function scope I 
used const scope.

In D, the type `T[]` is not an array like in C, but a slice, 
containing a pointer to some data and an integer indicating the 
array's length. So when you pass it to a function by value, only 
the pointer and length are copied, not the data itself.

You can read more about D's slices in this article: 
https://dlang.org/articles/d-array-article.html