70 lines
2.7 KiB
Racket
70 lines
2.7 KiB
Racket
#lang type-expander/lang
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#|hyper-literate #:♦ #:no-auto-require (dotlambda/unhygienic
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. type-expander/lang)
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♦chunk[<*>|#
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(provide builder-τ)
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(require racket/require
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(for-syntax (subtract-in racket/base subtemplate/override)
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racket/list
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racket/function
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subtemplate/override))
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(struct (T) Some ([f : T]))
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(struct (T) None ([f : T]))
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(define-type-expander BinaryTree
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(syntax-parser
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[(_ leafⱼ …)
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;; TODO: implement BinaryTree.
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#'(List leafⱼ …)]))
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(define-type-expander builder-τ
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(syntax-parser
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[(_ n m)
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#:with (Nᵢ …) (range n)
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#:with (Mⱼ …) (range m)
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#:with ((Kᵢⱼ …) …) (map (const (Kⱼ …)) (Nᵢ …))
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#:with ((Xᵢⱼ …) …) (map (const (Xⱼ …)) (Nᵢ …))
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#:with ((Nᵢⱼ …) …) (map (λ (ni) (map (const ni) (Xⱼ …))) (Nᵢ …))
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(define Ns (Nᵢ …))
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(define Ms (Mⱼ …))
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;(define/with-syntax exceptⱼ (remove Mⱼ Ns)) …
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; (define/with-syntax ((exceptᵢⱼ …) …)
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; (map (const (exceptⱼ …)) (Nᵢ …)))
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(define/with-syntax (exceptᵢ …) ((remove Nᵢ Ns) …))
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(define/with-syntax ((exceptᵢⱼ …) …)
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((map (const (remove Nᵢ Ns)) Ms) …))
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#'(∀ ((?@ Kⱼ Xⱼ) …)
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(→ (?@ Kⱼ Xⱼ) …
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(BinaryTree
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(U (Pairof Nᵢ
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;; If Kⱼ is Nᵢ, then {∩ Kᵢⱼ {U . exceptᵢⱼ}} will
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;; Nothing. We multiply the Nothing together by
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;; building a List out of them (a single occurrence
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;; of Nothing should collapse the list), so that the
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;; result should be Nothing only if there is no Kⱼ
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;; equal to Nᵢ. To force TR to propagate Nothing as
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;; much as possible, we intersect it with
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;; (None Any), which should be a no-op, but makes
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;; sure the simplifier which runs with ∩ kicks in.
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;; Therefore, the (None whatever) should appear only
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;; if there is indeed no key provided for that leaf.
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(∩ (None (List {∩ Kᵢⱼ {U . exceptᵢⱼ}} …))
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(None Any)))
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(∩ (Pairof Kᵢⱼ (Some Xᵢⱼ))
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(Pairof Nᵢⱼ Any))
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…)
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…)))]))
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; ../../../.racket/snapshot/pkgs/typed-racket-lib/typed-racket/types/overlap.rkt:40:0: mask-accessor: contract violation
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; expected: mask?
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; given: #f
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(define-type τ-4-2 (builder-τ 4 2))
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;]
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