64 lines
2.3 KiB
Scheme
64 lines
2.3 KiB
Scheme
(module useful-code (lib "frtime.ss" "frtime")
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(require (lib "string.ss")
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(lib "contract.ss")
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(lib "list.ss"))
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(provide (all-defined))
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; Keeps a list of the last n values of a behavior
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(define/contract history-e (case-> (event? . -> . any)
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(event? number? . -> . any))
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(case-lambda [(stream)
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(define ((add-to-complete-hist x) hist) (append hist (list x)))
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(accum-e (stream . ==> . add-to-complete-hist) empty)]
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[(stream n)
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(define ((add-to-short-hist x) hist) (append (if (< (length hist) n) hist (rest hist)) (list x)))
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(accum-e (stream . ==> . add-to-short-hist) empty)]))
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(define/contract history-b (case-> (event? . -> . any)
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(event? number? . -> . any))
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(case-lambda [(stream) (hold (history-e stream) empty)]
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[(stream n) (hold (history-e stream n) empty)]))
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; Counts number of events on an event stream
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(define/contract count-b (event? . -> . any)
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(lambda (stream)
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(hold (accum-e (stream . -=> . add1) 0) 0)))
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; Keeps track of the largest value seen on a stream
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(define/contract largest-val-b (event? . -> . any)
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(lambda (stream)
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(hold (accum-e (stream
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. ==> .
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(lambda (last)
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(lambda (x)
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(if (> x last) x last))))
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-inf.0))))
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; Keeps track of the smallest value seen on a stream
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(define/contract smallest-val-b (event? . -> . any)
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(lambda (stream)
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(hold (accum-e (stream
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. ==> .
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(lambda (last)
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(lambda (x)
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(if (< x last) x last))))
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+inf.0))))
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; Matches a sequence of items in a list to event pings
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(define/contract sequence-match? ((listof any/c) . -> . any)
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(lambda (seq evs)
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(equal? seq (history-b evs (length seq)))))
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; Cheap printf for behaviors
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(define printf-b format)
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; Flattens a list
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(define (flatten x)
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(cond ((empty? x) '())
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((and (list? x)
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(list? (first x)))
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(append (flatten (car x)) (flatten (cdr x))))
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(else (list x))))) |