Re: error trapping
james anderson scripsit: > one intrinsic problem with java parsers is that the java control model forces > exceptions to unwind from the initiator's dynamic context before the handler > obtains control. It is no accident that C++ and Java have termination semantics only for their exceptions. Unfortunately I cannot find a citation to this story, but it is instructive. Mesa, a dialect of Pascal with modules, exceptions, and many other things, was the language of a group at Xerox PARC. Its exceptions were defined with resumption semantics. Over the course of many years of large-scale development, including the Xerox Star and ViewPoint document workstations, it was found that wherever resumption was actually employed, it was invariably buggy. One by one, resumptive exception handlers were tracked down and removed, until in the end nothing was left but termination. The essential problem with resumption, IMHO, is that it breaks encapsulation: the resumptive handler is written by the author of the calling routine, but runs as a friend of the called routine. To work correctly, then, the caller must know everything about the callee. -- John Cowan cowan@c... I am a member of a civilization. --David Brin xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1 To unsubscribe, mailto:majordomo@i... the following message; unsubscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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