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Mon, 26 May 2003 11:44:16 +0200
Gnus/5.090004 (Oort Gnus v0.04) Emacs/21.3.50 (sparc-sun-solaris2.8)
Bill Schottstaedt <address@hidden> writes:
> Why doesn't Scheme have "continuation?"?
A continuation is just a procedure. It is not guaranteed to be
distinguishable from an "ordinary" procedure.
A Scheme compiler can transform programs that use
call-with-current-continuation in a way that just "ordinary"
procedures are passed, i.e. no magic "continuation object" occurs.
Therefore, a program should not depend on this distinction.
> (catch 'got-c-g
> (lambda ()
> (do ((i 0 (1+ i)))
> ((= i 100))
> (if (c-g?) ; returns #t if C-g was typed
> (lambda (return)
> (throw 'got-c-g return))))
> (display (format #f "back again: ~A" i))
> (sleep 1)))
> (lambda args
> (display (format #f "caught C-g: ~A" args))
> (if (continuation? (cadr args))
> ((cadr args) #f))))
Matthias Koeppe -- http://www.math.uni-magdeburg.de/~mkoeppe