> If the compiler knows about multidimensional arrays, it's easy to make those checks once at FOR loop entry. Or you could just use a little unsafe code to imp

> If the compiler knows about multidimensional arrays, it's easy to make those checks once at FOR loop entry. Or you could just use a little unsafe code to implement iterators and matrix multiplication on top of the array, and then never use unsafe with the matrices anyway. This is what gets done with regular arrays and vectors. Directly indexing these types is pretty rare. You would do the same with matrices. "Put it in the language" is not a solution for everything, especially when the tools are there to build it with almost the same level of ergonomics. Requiring unsafe for designing some kinds of abstractions is not a bad thing. There's no need to shove everything into the language if it can be implemented as a library with a smattering of unsafe code. It's almost equivalent, really. Making a mistake when writing this unsafe code and making a mistake in the builtin optimization are mostly equivalent risks. There's nothing inherently worse about doing it as a library, aside from the minor issue that the indexing syntax isn't so great.