Guarantees on order of evaluation?

[Palli]

I believe everything is evaluated left-to-right (that’s a guarantee except if you control with parenthesis, and also precedence rules apply), except for, yes (there’s a good reason for this, to allow it undefined, but I think in practice for now, if may also be left-to-right):

The only thing I have been able to find is that the order of evaluations in a chained comparison is not defined.

I recall however one suggestion to break that rule for 2.0 (may never be implemented, meant for matrices if I recall, the title is misleading, doesn’t justify this issue):

Parse 1 + 2 + 3 as +(1, +(2, 3))

You can also change to more optimal way of evaluating with a macro (for matrix multiplies, then data dependent, I forget the package that implements it, maybe those in the following discussion, except they are outdated).

Why is multiplication A*B*C left-associative (`foldl`) not right-associative (`foldr`)?

This behaviour is a bit surprising: julia> A = randn(50,50); x = randn(50); julia> @btime A*A*x; 10.064 μs (3 allocations: 20.17 KiB) julia> @btime A*(A*x); 736.336 ns (2 allocations: 1.06 KiB) julia> @btime (A*A)*x; 11.066 μs (3 allocations: 20.17 KiB) I’m curious on the design choice, as matrix * vector is much more common than say vector’ * matrix.

So what I really want is short-circuit evaluation for multiplication 3, which doesn’t seem to exist?

Seems would be doable with a macro.