https://github.com/pyrocat101/w

Hindley-Milner type inference.
https://github.com/pyrocat101/w

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Hindley-Milner type inference.

• Host: GitHub
• URL: https://github.com/pyrocat101/w
• Owner: pyrocat101
• License: epl-1.0
• Created: 2014-02-22T06:56:29.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2014-03-31T08:10:08.000Z (over 10 years ago)
• Last Synced: 2024-04-15T02:49:05.220Z (7 months ago)
• Language: Clojure
• Homepage:
• Size: 243 KB
• Stars: 5
• Watchers: 2
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Algorithm W

An implementation of algorithm W for Hindley-Milner polymorphic type inference.

Use the Source, Luke!

``` clojure

(infer '+)

; => (:int -> (:int -> :int))

(infer '(+ 1 1))

; => :int

(infer '(fn [x] x))

; => (t0 -> t0)

(infer '(fn [x y] (+ x y)))

; => (:int -> (:int -> :int))

(infer '(let [f (fn [x] x)] f))

; => (t0 -> t0)

(infer '(if true 42 (+ 333 333)))

; => :int

(infer '())

; => (:list t0)

(infer '(empty? ()))

; :bool

(infer '(empty? (cons 1 ())))

; => :bool

(infer '(cons 1 ()))

; => (:list :int)

(infer '(first (cons 1 ())))

; => :int

(infer '(rest (cons 1 ())))

; => (:list :int)

(infer

 '(let [fact (fix

              (fn [fact x]

                (if (= x 1)

                  1

                  (* x (fact (- x 1))))))]

    (fact 10)))

; => :int

;; Tests used in `infer.ss` by Yin Wang

(infer '(fn [f x] (f x)))

; => ((t0 -> t1) -> (t0 -> t1))

(infer '(fn [f x] (f (f x))))

; => ((t0 -> t0) -> (t0 -> t0))

(infer '(fn [m n f x] ((m (n f)) x)))

;; => ((t0 -> (t1 -> t2)) -> ((t3 -> t0) -> (t3 -> (t1 -> t2))))

(infer '((fn [f] (f 1)) (fn [v] v)))

;; => :int

(def S '(fn [x y z] ((x z) (y z))))

(def K '(fn [x y] x))

(infer S)

; => ((t0 -> (t1 -> t2)) -> ((t0 -> t1) -> (t0 -> t2)))

(infer `(~S ~K))

; => ((t0 -> t1) -> (t0 -> t0))

(infer `((~S ~K) ~K))

; => (t0 -> t0)

```

## References

1. Martin Grabmüller, Algorithm W Step by Step

2. Luis Damas and Robin Milner, Principal Type-Schemes for Functional Programs

## License

Copyright © 2014 Linjie Ding

Distributed under the Eclipse Public License either version 1.0 or (at your

option) any later version.