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@ -36,32 +36,46 @@
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(define vec (match quad-or-index
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[(? quad? q) (make-query-index q)]
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[idx idx]))
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(define (next-occurrence-between pred lidx ridx)
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(cond
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[(or (not lidx) (not ridx)) ridx]
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;; we are searching between, so add 1 to left idx
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[(for/first ([idx (in-range (add1 lidx) ridx)]
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#:when (pred (vector-ref vec idx)))
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idx)]
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[else (vector-length vec)]))
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(for/fold ([vidx 0]
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[maxidx (vector-length vec)]
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#:result (and vidx (vector-ref vec vidx)))
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([query-piece (in-list (parse-query query-str))]
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#:break (not vidx))
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(match query-piece
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[(cons pred 'this)
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;; find the querying quad, and from there search backward
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;; todo: `this` should also cut down the domain of searching
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(for/first ([vidx (in-range (vector-memq starting-q vec) -1 -1)]
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#:when (pred (vector-ref vec vidx)))
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vidx)]
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[(cons pred 'last) (error 'unimplemented)]
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[(cons pred 'prev) (error 'unimplemented)]
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[(cons pred 'next) (error 'unimplemented)]
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[(cons pred count)
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(for/fold ([vidx vidx]
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;; sub 1 because return values add 1
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;; and final result should be location of matching quad
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#:result (and vidx (sub1 vidx)))
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([seen (in-range count)]
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#:break (not vidx))
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(for/first ([vidx (in-range vidx (vector-length vec))]
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(match-define (cons pred count) query-piece)
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(define res-idx
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(match count
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[(or (== 'this eq?) (== 'last eq?))
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;; find a starting point, then search backward
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(for/first ([vidx (in-range (if (eq? count 'this)
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;; start at querying quad
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(vector-memq starting-q vec)
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;; start at end
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(sub1 maxidx)) -1 -1)]
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#:when (pred (vector-ref vec vidx)))
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;; add 1 so on next iteration, we can find next matcher
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;; and won't re-find this one immediately
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(add1 vidx)))])))
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vidx)]
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[(== 'prev eq?) (error 'unimplemented)]
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[(== 'next eq?) (error 'unimplemented)]
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[count
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(for/fold ([vidx vidx]
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;; sub 1 because return values add 1
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;; and final result should be location of matching quad
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#:result (and vidx (sub1 vidx)))
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([seen (in-range count)]
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#:break (not vidx))
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(for/first ([vidx (in-range vidx maxidx)]
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#:when (pred (vector-ref vec vidx)))
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;; add 1 so on next iteration, we can find next matcher
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;; and won't re-find this one immediately
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(add1 vidx)))]))
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(values res-idx (next-occurrence-between pred res-idx maxidx))))
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(module+ test
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(require rackunit)
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