30 lines
914 B
Common Lisp
30 lines
914 B
Common Lisp
(lib 'sequences)
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(define input-stream null)
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(define output-stream "")
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;;---------------------------
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;; character I/O simulation
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;; --------------------------
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(define (read-char) (next input-stream)) ;; #f if EOF
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(define (write-char c) (when c (set! output-stream (string-append output-stream c))))
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(define (init-streams sentence)
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(set! input-stream (procrastinator sentence))
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(set! output-stream ""))
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;;---------------------------------
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;; task , using read-char/write-char
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;;----------------------------------
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(define (flop) ; reverses, and returns first non-alpha after word, or EOF
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(define c (read-char))
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(if (string-alphabetic? c) (begin0 (flop) (write-char c)) c))
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(define (flip)
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(define c (read-char))
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(if (string-alphabetic? c) (begin (write-char c) (flip)) c))
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(define (task sentence)
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(init-streams sentence)
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(while (and (write-char (flip)) (write-char (flop))))
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output-stream )
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