(alt & key-pred-forms)
Takes key+pred pairs, e.g. (s/alt :even even? :small #(< % 42)) Returns a regex op that returns a map entry containing the key of the first matching pred and the corresponding value. Thus the 'key' and 'val' functions can be used to refer generically to the components of the tagged return
;; unlike `or`, `alt` works on sequence elements, not on values themselves!
user=> (s/conform (s/alt :num number? :key keyword?) 3)
:clojure.spec.alpha/invalid
user=> (s/conform (s/alt :num number? :key keyword?) [3])
[:num 3]
;; compare this to `or`:
user=> (s/conform (s/or :num number? :key keyword?) 3)
[:num 3]
user=> (s/conform (s/or :num number? :key keyword?) [3])
:clojure.spec.alpha/invalid