67 lines
1.7 KiB
Scheme
67 lines
1.7 KiB
Scheme
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; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
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; Tiny image and simple I/O test system
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; This prints `Hello' and the first command argument, if any, then reads
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; a line from standard input and prints it to standard output.
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(define (start arg in out error-out resumer-records)
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(write-string "Hello " out)
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(if (vector? arg)
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(if (< 0 (vector-length arg))
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(write-string (vector-ref arg 0) out)))
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(collect)
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(collect)
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(newline out)
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(write-string (read-string in) out)
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(newline out)
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0)
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(define first? #t)
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(define (write-string string . channel-option) ; test n-ary procedures
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(channel-maybe-write string
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0
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(string-length string)
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(car channel-option)))
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(define (newline channel)
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(write-string "
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" channel))
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(define (read-string in)
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((lambda (buffer)
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(letrec ((loop (lambda (have)
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((lambda (got)
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(if (eq? got (eof-object))
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"eof"
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((lambda (len)
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(if len
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((lambda (string)
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(copy-string! buffer string len)
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string)
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(make-string len #\space))
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(loop (+ have got))))
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(has-newline buffer have got))))
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(channel-maybe-read buffer have (- 80 have) #f in)))))
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(loop 0)))
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(make-string 80 #\space)))
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(define (has-newline string start count)
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(letrec ((loop (lambda (i)
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(if (= i count)
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#f
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(if (char=? #\newline
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(string-ref string (+ start i)))
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(+ start i)
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(loop (+ i 1)))))))
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(loop 0)))
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(define (copy-string! from to count)
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(letrec ((loop (lambda (i)
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(if (< i count)
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(begin
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(string-set! to i (string-ref from i))
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(loop (+ i 1)))))))
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(loop 0)))
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