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94 lines
3.3 KiB
Racket
94 lines
3.3 KiB
Racket
#lang debug racket/base
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(require racket/contract racket/function rackunit)
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(struct $point (x y) #:transparent #:mutable)
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(struct $size (width height) #:transparent #:mutable)
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(struct $rect (origin size) #:transparent #:mutable)
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(struct $quad (posn char) #:transparent #:mutable)
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(define/contract (posn-add p0 p1)
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($point? $size? . -> . $point?)
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($point (+ ($point-x p0) ($size-width p1)) (+ ($point-y p0) ($size-height p1))))
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(define/contract (size char)
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($quad? . -> . $size?)
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($size 1 1))
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(define/contract (advance char)
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($quad? . -> . $size?)
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($size 1 0))
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(define pass/c ((listof $quad?) . -> . (listof $quad?)))
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(define/contract (quadify str)
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(string? . -> . (listof $quad?))
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(for/list ([c (in-string str)])
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($quad #f c)))
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(define/contract (make-compiler . passes)
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(() #:rest (listof pass/c)
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. ->* . (string? . -> . (listof $quad?)))
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(apply compose1 (reverse (cons quadify passes))))
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(define-syntax-rule (define-pass (PASS-NAME ARG)
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#:precondition PRECOND-PROC
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#:postcondition POSTCOND-PROC
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EXPRS ...)
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(define/contract (PASS-NAME ARG)
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pass/c
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(unless (PRECOND-PROC ARG)
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(error 'precondition-failed))
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(define res (let () EXPRS ...))
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(unless (POSTCOND-PROC res)
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(error 'postcondition-failed))
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res))
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(define (min-x rect) ($point-x ($rect-origin rect)))
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(define (width rect) ($size-width ($rect-size rect)))
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(define (max-x rect) (+ (min-x rect) (width rect)))
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(define (min-y rect) ($point-y ($rect-origin rect)))
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(define (height rect) ($size-height ($rect-size rect)))
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(define (max-y rect) (+ (min-y rect) (height rect)))
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(define/contract (rect-contains-point? rect pt)
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($rect? $point? . -> . boolean?)
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(and (<= (min-x rect) ($point-x pt) (max-x rect))
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(<= (min-y rect) ($point-y pt) (max-y rect))))
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(define/contract (rect-contains-rect? outer inner)
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($rect? $rect? . -> . boolean?)
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(and (rect-contains-point? outer ($rect-origin inner))
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(rect-contains-point? outer ($point (max-x inner) (max-y inner)))))
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(define (has-position? q) (not (eq? ($quad-posn q) #false)))
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(define-pass (layout qs)
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#:precondition (λ (qs) (andmap (λ (q) (not (has-position? q))) qs))
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#:postcondition (λ (qs) (andmap has-position? qs))
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(define frame ($rect ($point 0 0) ($size 5 30)))
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(define (quad-fits? q posn)
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(define q-size (size q))
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(define quad-rect ($rect posn q-size))
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(and (rect-contains-rect? frame quad-rect) posn))
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(for/fold ([posn ($point 0 0)]
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#:result qs)
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([q (in-list qs)])
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(define first-posn-on-next-line ($point 0 (add1 ($point-y posn))))
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(define winning-posn (or (ormap (λ (posn) (quad-fits? q posn)) (list posn first-posn-on-next-line)) (error 'no-posn-that-fits)))
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(set-$quad-posn! q winning-posn)
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(posn-add winning-posn (advance q))))
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(define compile (make-compiler layout))
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(check-equal? (compile "Hello world")
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(list
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($quad ($point 0 0) #\H)
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($quad ($point 1 0) #\e)
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($quad ($point 2 0) #\l)
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($quad ($point 3 0) #\l)
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($quad ($point 4 0) #\o)
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($quad ($point 0 1) #\space)
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($quad ($point 1 1) #\w)
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($quad ($point 2 1) #\o)
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($quad ($point 3 1) #\r)
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($quad ($point 4 1) #\l)
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($quad ($point 0 2) #\d))) |