Re: [Chicken-users] with-*-*-port

[Felix Winkelmann]

Tony Garnock-Jones wrote:
> > (define with-input-from-port
> >  (let ((values values))
> >    (lambda (port thunk)
> >      (let ((old ##sys#standard-input))
> >        (##sys#dynamic-wind
> >         (lambda () (set! ##sys#standard-input port))
> >         thunk
> >         (lambda () (set! ##sys#standard-input old))) ) ) ) )
>
>
> Perhaps this would be better capturing standard-input on each
> transition, rather than just the first?
>
> (Untested code follows)
>
> (define with-input-from-port
>   (let ((values values))
>     (lambda (inner thunk)
>       (let ((outer '*))
>         (##sys#dynamic-wind
>          (lambda ()
>            (set! outer ##sys#standard-input)
>            (set! ##sys#standard-input inner))
>          thunk
>          (lambda ()
>            (set! inner ##sys#standard-input)
>            (set! ##sys#standard-input outer)))))))
>
> Does this make sense, or is it too paranoid?

It *is* paranoid, but it's the safest method.


cheers,
felix


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