gistfile1.txt

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# Clojureの型推論器

## typelogicの紹介

[@halcat0x15a](https://twitter.com/halcat0x15a)

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# 型の話

```clojure
(class "") ; => java.lang.String
(class 0)  ; => java.lang.Long

(defn first [coll]
  (clojure.lang.RT/first coll))
```

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# 型推論器の利用

型検査

```clojure
=> (defn contains0? [^String s]
     (.contains s 0))

=> (check (quote (fn [^String s] (.contains s 0))))

Unhandled clojure.lang.ExceptionInfo
   type mismatch;
   {:op [::fn ([[CharSequence] boolean])],
    :args (0)}
```

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# typelogicの特徴

```clojure
; core.typed
(ann twice [Number -> Number])
(defn twice [n]
  (* n 2))
(check-ns)
(cf twice) ; => (clojure.core.typed/IFn [Number -> Number])

; typelogic
(check (quote (fn [n] (* n 2)))) ; => [::fn ([long] long) ([double] double) ([Object] Number)]

(check {(quote *) [::fn ([Number Number] Number)]}
       (quote (fn [n] (* n 2)))) ; => [::fn ([Number] Number)]

(check (quote str))              ; => [::var str [::fn ([] String) ([Object] String) ([Object [::seq]] String)]]
```

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# これから

* special formの網羅
* 構造的な型のサポート
* 推論器を使ったツールの作成