Getting Clojure

Spec’ing Collections

We can also create specs for the various collections. The most basic here is coll-of, which specifies a collection of something:

;; Something like '("Alice" "In" "Wonderland").

(def coll-of-strings (s/coll-of string?))

;; Or a collection of numbers or strings, perhaps ["Emma" 1815 "Jaws" 1974]

(def coll-of-n-or-s (s/coll-of n-or-s))

To produce tighter specifications on collections, we can reach for cat. Essentially cat lets you specify this should follow that in a collection. For example, if we wanted to match only four-element collections consisting of alternating strings and numbers we could say this:

(def s-n-s-n (s/cat :s1 string? :n1 number? :s2 string? :n2 number?))

(s/valid? s-n-s-n ["Emma" ...