Liquid's boolean logic does not support not, so is not functionally complete

[Blaisorblade]

Liquid should support not — not only because it is the obvious thing to do, but also because it is required to write arbitrary boolean conditions. unless is not sufficient for nested negations --- @nickpearson shows how to compile not by hand in this comment, and the amount of extra needed code is significant.

Moreover, the documentation claims:

Liquid has access to all of the logical and comparison operators.

but because of the absence of not, that's not true.

(I know that there is #138, but it was closed without sufficient discussion).

[fw42]

I agree that it would be nice to have (same way having support for parentheses would be nice to have). Unfortunately it's not on our roadmap at the moment. But feel free to submit a PR and we will check it out.

[fw42]

I'm reopening the other one