This is why we've ended up at a mixed approach. Types in Julia are used to "distinguish between things". Multiple dispatch then is a great system for defining r

This is why we've ended up at a mixed approach. Types in Julia are used to "distinguish between things". Multiple dispatch then is a great system for defining rules that are specific to groups: `AbstractMatrix` types have non-commutative rulesets, and we then let them have different rules from `Real` and let subtyping control at a finer grain what rules apply to which pieces, and what rules apply when you combine them.