That's true. I think I was just paranoid about how slingshot was set up to test truthiness. I know the README explicitly states that a predicate selector must take one argument and return a truthy value, but given that selectors might at some point resolve into all kinds of things going forward (new slingshot syntax, some creative use of a function generator, etc) I thought being explicit would be more clearly reflect the intent of passing a predicate to slingshot as a selector.

Again, happy to defer to you if you have a strong opinion about it, though if that's the case I'd be genuinely interested to hear your reasoning.