forgot to add maybe.rkt and either.rkt
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#lang turnstile
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(provide Left
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Right
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Either
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left
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right
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partition/either)
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(require "core-types.rkt")
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(require "core-expressions.rkt")
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(require "for-loops.rkt")
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(require "list.rkt")
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(define-constructor* (left : Left v))
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(define-constructor* (right : Right v))
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(define-type-alias (Either A B)
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(U (Left A)
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(Right B)))
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(define (∀ (X Y Z) (partition/either [xs : (List X)]
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[pred : (→fn X (Either Y Z))]
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-> (Tuple (List Y) (List Z))))
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(for/fold ([acc (Tuple (List Y) (List Z)) (tuple (list) (list))])
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([x xs])
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(define y-or-z (pred x))
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(match y-or-z
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[(left (bind y Y))
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(tuple (cons y (select 0 acc))
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(select 1 acc))]
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[(right (bind z Z))
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(tuple (select 0 acc)
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(cons z (select 1 acc)))])))
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@ -0,0 +1,37 @@
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#lang turnstile
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(provide Maybe
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None
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None*
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Some
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some
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none)
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(require "core-types.rkt")
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(define-constructor* (none* : None*))
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(define-constructor* (some : Some v))
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(define-type-alias None (None*))
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(define none : None
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(none*))
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(define-type-alias (Maybe X)
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(U None
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(Some X)))
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#;(define (∀ (X Y) (partition/maybe [xs : (List X)]
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[pred : (→fn X (Maybe Y))]
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-> (Tuple (List Y) (List X))))
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#f)
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#;(require (only-in "core-expressions.rkt" match error discard)
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"prim.rkt")
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#;(define (∀ (X) (unwrap! [x : (Maybe X)] -> (Maybe X)))
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(match x
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[(some discard)
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(error "some")]
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[none
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(error "none")]))
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