39 lines
1.5 KiB
Scheme
39 lines
1.5 KiB
Scheme
(define (call-with-input-file s p) "open an input file s and apply a function to it, then close the file"
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(let ((inport (open-input-file s)))
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(if (eq? inport #f)
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#f
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(let ((res (p inport)))
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(close-input-port inport)
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res))))
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(define (call-with-output-file s p) "open an output file s and apply a function to it, then close the file"
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(let ((outport (open-output-file s)))
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(if (eq? outport #f)
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#f
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(let ((res (p outport)))
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(close-output-port outport)
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res))))
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(define (with-input-from-file s p) "open an input file s and run a function while it's open"
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(let ((inport (open-input-file s)))
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(if (eq? inport #f)
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#f
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(let ((prev-inport (current-input-port)))
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(set-input-port inport)
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(let ((res (p)))
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(close-input-port inport)
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(set-input-port prev-inport)
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res)))))
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(define (with-output-to-file s p) "open an output file s and run a function while it's open"
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(let ((outport (open-output-file s)))
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(if (eq? outport #f)
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#f
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(let ((prev-outport (current-output-port)))
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(set-output-port outport)
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(let ((res (p)))
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(close-output-port outport)
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(set-output-port prev-outport)
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res)))))
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