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#lang debug racket
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(require quad/base "struct.rkt")
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(provide (all-defined-out))
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(define (make-linear-index q)
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(cons q (append-map make-linear-index (quad-elems q))))
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(define (string->pred str)
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(match str
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["doc" doc-quad?]
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[(or "section" "sec" "s") section-quad?]
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[(or "page" "pg" "p") page-quad?]
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[(or "column" "col" "c") column-quad?]
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[(or "block" "b") block-quad?]
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[(or "line" "ln" "l") line-quad?]))
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(define (parse-query str)
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(for/list ([piece (in-list (string-split str ":"))])
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(match (regexp-match #px"^(.*)\\[(.*?)\\]$" piece)
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[#false (cons (string->pred piece) #false)]
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[(list all name arg) (cons (string->pred name) (or (string->number arg)
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(string->symbol arg)))])))
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(define (query q query-str)
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(for/fold ([qs (make-linear-index q)]
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#:result (and qs (car qs)))
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([query-piece (in-list (parse-query query-str))])
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(match-define (cons pred count) query-piece)
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(let loop ([qs qs][seen 0])
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(define maybe-tail (memf pred qs))
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(and maybe-tail
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(let ([seen (add1 seen)])
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(cond
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[(= seen count) maybe-tail]
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[else (loop (cdr maybe-tail) seen)]))))))
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(module+ test
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(require rackunit)
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(define counter 0)
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(define-syntax-rule (factory type proc)
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(make-quad #:type type
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#:elems (for/list ([i (in-range 3)])
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(set! counter (add1 counter))
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(define new-q (proc))
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(quad-update! new-q
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[tag (format "~a[~a]-~a" 'proc counter (gensym))])
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(hash-set! (quad-attrs new-q) 'count counter)
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new-q)))
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(define (line) (make-quad #:type line-quad))
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(define (block) (factory block-quad line))
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(define (col) (factory column-quad block))
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(define (page) (factory page-quad col))
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(define (sec) (factory section-quad page))
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(define (count q) (quad-ref q 'count))
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(define doc (factory doc-quad sec))
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(check-equal? (count (query doc "sec[2]")) 242)
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(check-equal? (count (query doc "sec[2]:pg[1]")) 162)
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(check-equal? (count (query doc "sec[2]:pg[1]:ln[3]")) 128))
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