Path: utzoo!utgpu!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!purdue!mailrus!cornell!uw-beaver!uoregon!will
From: will@uoregon.uoregon.edu (William Clinger)
Newsgroups: comp.lang.scheme
Subject: Re: Re : unwind-protect
Message-ID: <2917@uoregon.uoregon.edu>
Date: 3 Oct 88 22:20:36 GMT
References: <16407@shemp.CS.UCLA.EDU> <19881003111852.6.MAEDA@PELE.ACA.MCC.COM>
Reply-To: will@fog.UUCP (William Clinger)
Organization: University of Oregon, Computer Science, Eugene OR
Lines: 13

>Hmm.  How would unwind-protect be expressed with just call/cc?

UNWIND-PROTECT is trivial to implement in terms of DYNAMIC-WIND, which can
be implemented in terms of CALL-WITH-CURRENT-CONTINUATION provided the
Scheme system permits CALL-WITH-CURRENT-CONTINUATION to be redefined,
uses close-coded calls to CALL-WITH-CURRENT-CONTINUATION for all captures
of a continuation, and contains no pre-captured continuations.

An implementation appears in Haynes and Friedman, Embedding Continuations
in Procedural Objects, TOPLAS 9, 4 (October 1987), pages 582-598.

Peace,
William Clinger