CAS Best Practices

[ChrisRackauckas]

julia> using Symbolics
julia> Term(sqrt,[2])
sqrt(2)

I don’t get why you’d work harder than that. You can build any expression to be lazily like that, or use @register on others.

@stevengj

This doesn’t work if x is an array — zero(x) * x will throw if x is not a square matrix. In the context of rings it is fine, of course, though it still won’t be equivalent to x-x for square matrices that may contain non-finite values.

I thought the reason for it was because the poster wanted “a zero in the type of x”:

@carette

I was warning that x−xx-x is tricky. It’s actually fairly safe to transform it to 0∗x0*x . For one, that’s type-safe, in the sense that xx is still around, so you know the result’s type properly. (Polymorphic 00 is a major pain.)

In which case trying to get 0 * x as they posted is an X-Y problem: just writing it as zero(x) is more direct and means what they actually meant using Base Julia functionality.