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strengthen typing on `shift`

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pull/3/head
Matthew Butterick 9 years ago
parent 124b0f5597
commit 3d6b75699a
1 changed files with 14 additions and 14 deletions
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28
typed/sugar/list.rkt
Unescape Escape View File

@ -17,7 +17,7 @@
(for/fold: ([current-list : (Listof A) empty]
[list-of-lists : (Listof (Listof A)) empty]
[negating? : Boolean #f])
([x (in-list xs)])
([x (in-list xs)])
(define current-pred (if negating? (λ: ([x : A]) (not (pred x))) pred))
(if (current-pred x)
(values (cons x current-list) list-of-lists negating?)
@ -37,8 +37,8 @@
[(xs pred force?)
(define-values (last-list list-of-lists)
(for/fold:
([current-list : (Listof A) empty][list-of-lists : (Listof (Listof A)) empty])
([x (in-list xs)])
([current-list : (Listof A) empty][list-of-lists : (Listof (Listof A)) empty])
([x (in-list xs)])
(if (pred x)
(values (cons x null) (if (not (empty? current-list))
(cons (reverse current-list) list-of-lists)
@ -55,7 +55,7 @@
(All (A) ((Listof A) (A -> Boolean) -> (Listof (Listof A))))
(define-values (last-list list-of-lists)
(for/fold: ([current-list : (Listof A) empty][list-of-lists : (Listof (Listof A)) empty])
([x (in-list xs)])
([x (in-list xs)])
(if (pred x)
(values empty (cons (reverse (cons x current-list)) list-of-lists))
(values (cons x current-list) list-of-lists))))
@ -74,7 +74,7 @@
[(xs len force?)
(define-values (last-list list-of-lists)
(for/fold: ([current-list : (Listof A) empty][list-of-lists : (Listof (Listof A)) empty])
([x (in-list xs)][i (in-naturals)])
([x (in-list xs)][i (in-naturals)])
(if (= (modulo (add1 i) len) 0)
(values empty (cons (reverse (cons x current-list)) list-of-lists))
(values (cons x current-list) list-of-lists))))
@ -87,7 +87,7 @@
(All (A) ((Listof A) (A -> Boolean) -> (Listof (Listof A))))
(define-values (last-list list-of-lists)
(for/fold: ([current-list : (Listof A) empty][list-of-lists : (Listof (Listof A)) empty])
([x (in-list xs)])
([x (in-list xs)])
(if (pred x)
(values empty (if (not (empty? current-list))
(cons (reverse current-list) list-of-lists)
@ -166,25 +166,25 @@
(define/typed+provide shift
(case-> ((Listof Any) (U Integer (Listof Integer)) -> (Listof Any))
((Listof Any) (U Integer (Listof Integer)) Any -> (Listof Any))
((Listof Any) (U Integer (Listof Integer)) Any Boolean -> (Listof Any)))
(All (A) (case-> ((Listof (Option A)) (U Integer (Listof Integer)) -> (U (Listof (Option A)) (Listof (Listof (Option A)))))
((Listof (Option A)) (U Integer (Listof Integer)) (Option A) -> (U (Listof (Option A)) (Listof (Listof (Option A)))))
((Listof (Option A)) (U Integer (Listof Integer)) (Option A) Boolean -> (U (Listof (Option A)) (Listof (Listof (Option A)))))))
(case-lambda
[(xs shift-amount-or-amounts)
(shift xs shift-amount-or-amounts #f #f)]
[(xs shift-amount-or-amounts fill-item)
(shift xs shift-amount-or-amounts fill-item #f)]
[(xs shift-amount-or-amounts fill-item cycle)
(define/typed (do-shift xs how-far)
((Listof Any) Integer -> (Listof Any))
(define/typed (do-shift xs fill-item how-far)
(All (A2) ((Listof (Option A2)) (Option A2) Integer -> (Listof (Option A2))))
(define abs-how-far (abs how-far))
(cond
[(> abs-how-far (length xs)) (error 'shift "index is too large for list\nindex: ~a\nlist: ~v" how-far xs)]
[(= how-far 0) xs]
[(positive? how-far)
(append (make-list abs-how-far fill-item) (drop-right xs abs-how-far))]
((inst append (Option A2)) ((inst make-list (Option A2)) abs-how-far fill-item) (drop-right xs abs-how-far))]
;; otherwise how-far is negative
[else (append (drop xs abs-how-far) (make-list abs-how-far fill-item))]))
(if (list? shift-amount-or-amounts)
(map (λ:([amount : Integer]) (do-shift xs amount)) shift-amount-or-amounts)
(do-shift xs shift-amount-or-amounts))]))
((inst map (Listof (Option A)) Integer) (λ:([amount : Integer]) (do-shift xs fill-item amount)) shift-amount-or-amounts)
(do-shift xs fill-item shift-amount-or-amounts))]))

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