Translation of SICP make-rat, denom and numer operations to Clojure with the addition of Typed Clojure to define a "SicpRatio" type as an alias to a vector of size 2

sicpratio.clj

(ns complex-clojure.core
  (:require [clojure.core.typed :as t])
  (:use [clojure.core.typed :only [AnyInteger]]))

(t/def-alias SicpRatio (Vector* AnyInteger AnyInteger))

(t/ann make-rat [AnyInteger AnyInteger -> SicpRatio])
(defn make-rat [numer denom] [numer denom])

(t/ann denom [SicpRatio -> AnyInteger])
(defn denom [[_ denom]] denom)

(t/ann numer [SicpRatio -> AnyInteger])
(defn numer [[numer _]] numer)

;; cf is abbreviated from check form. It can be used to check our types

(t/cf (make-rat 1 5))
;; complex-clojure.core/SicpRatio

(comment
  ;; This fails the check because 1.1 is not an integer
  (t/cf (make-rat 1.1 5)))

(t/cf (numer (make-rat 1 5)))
;; (U java.lang.Long java.lang.Integer java.math.BigInteger java.lang.Byte java.lang.Short clojure.lang.BigInt)
;; AnyInteger is an alias for this Union

;; We don't need to construct with make-rat, anything that conforms to the type will do
(t/cf (numer [1 5]))

;; But our vector still needs to be the correct size
(comment
  (t/cf (numer [1 5 10]))
  ;; Errors with
  Actual type
        [(Value 1) (Value 5) (Value 10)]
  is not a subtype of Expected type
        complex-clojure.core/SicpRatio  clojure.core.typed/type-error (subtype.clj:24)
)