clojure.spec: `alt` vs `or` for sequence spec -


i'm following clojure.spec's guide (http://clojure.org/guides/spec). i'm confused difference between alt , or sequence spec.

for me 2 following examples work equally well. what's difference between two?

; use `alt` (s/def ::config (s/* (s/cat :prop string?                         :val (s/alt :s string? :b boolean?)))) (s/explain ::config ["-server" "foo" "-verbose" true "-user" 13])  ; use `or` (s/def ::config (s/* (s/cat :prop string?                         :val (s/or :s string? :b boolean?)))) (s/explain ::config ["-server" "foo" "-verbose" true "-user" 13])

s/alt concatenating nested regex specs using s/or specifies subsequence. in example doesn't make difference since not using nested regex specs. here example:

(s/def ::number-regex (s/* number?))  (s/def ::or-example (s/cat :nums (s/or :numbers ::number-regex)))  (s/valid? ::or-example [1 2 3]) ;;-> false (s/valid? ::or-example [[1 2 3]]) ;;-> true

as can see, or specifies sub-sequence in new regex context started, whereas alt specifies opposite:

(s/def ::alt-example (s/cat :nums (s/alt :numbers ::number-regex)))  (s/valid? ::alt-example [1 2 3]) ;;-> true (s/valid? ::alt-example [[1 2 3]]) ;;-> false

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