Just curious, what’s the meaning of the naming convention used in (I believe) reitit and malli, with ? before symbol names? Like ?foo ?
I think: "coerceable into foo"
Ahhh ok. Makes sense.
I read prefixed ? as a "maybe". This is symmetric to predicate notation having interrogative postfix ?.
?foo => maybe a foo
foo? => does foo exist?
(foo? ?foo) => maybe truthy or falsey.