25 lines
625 B
Plaintext
25 lines
625 B
Plaintext
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#lang racket
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;; draw a graph of cos and deriv^3(cos)
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(require plot)
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(define ((deriv f) x)
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(/ (- (f x) (f (- x 0.001))) 0.001))
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(define (thrice f) (lambda (x) (f (f (f x)))))
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(plot (list (function ((thrice deriv) sin) -5 5)
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(function cos -5 5 #:color 'blue)))
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;; Print the Greek alphabet
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(for ([i (in-range 25)])
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(displayln
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(integer->char
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(+ i (char->integer #\u3B1)))))
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;; An echo server
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(define listener (tcp-listen 12345))
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(let echo-server ()
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(define-values (in out) (tcp-accept listener))
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(thread (λ ()
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(copy-port in out)
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(close-output-port out)))
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(echo-server))
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