What would m[3] mean for a SIMD4x3 matrix type?
I guess it would have to be very different from the current import simd-types:
import simd
var m = float4x3() // A matrix of 4 columns, each column is a float3
let fourthColumn: float3 = m[3]
since according to the proposed SIMD protocol, the subscript that takes an Int returns a Scalar which I assume would be Float rather than SIMD3<Float>?
(Related separate thread here.)