167 lines
6.6 KiB
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167 lines
6.6 KiB
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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Converted with LaTeX2HTML 0.6.5 (Tue Nov 15 1994) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<HEAD>
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<TITLE>28.1.1. Error Terminology</TITLE>
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<meta name="description" value=" Error Terminology">
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<meta name="keywords" value="clm">
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<meta name="distribution" value="global">
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<P>
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<b>Common Lisp the Language, 2nd Edition</b>
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<BR> <HR><A NAME=tex2html4934 HREF="node263.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html4932 HREF="node261.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html4926 HREF="node261.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html4936 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html4937 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html4935 HREF="node263.html"> Classes</A>
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<B>Up:</B> <A NAME=tex2html4933 HREF="node261.html"> Programmer Interface Concepts</A>
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<B> Previous:</B> <A NAME=tex2html4927 HREF="node261.html"> Programmer Interface Concepts</A>
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<HR> <P>
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<H2><A NAME=SECTION003211000000000000000>28.1.1. Error Terminology</A></H2>
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<P>
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<img align=bottom alt="change_begin" src="gif/change_begin.gif"><br>
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<A NAME=ErrorTerminologySECTION>The</A>
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terminology used in this chapter to describe erroneous
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situations differs from the terminology used in the first edition.
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The new terminology involves <i>situations</i>;
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a situation is the evaluation of an expression in some
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specific context. For example, a situation might be the invocation of
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a function on arguments that fail to satisfy some specified
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constraints.
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<P>
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In the specification of the Common Lisp Object System, the behavior of programs in all situations
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is described, and the options available to the implementor are defined. No
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implementation is allowed to extend the syntax or semantics of the Object System except
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as explicitly defined in the Object System specification. In particular, no
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implementation is allowed to extend the syntax of the Object System in such a way that
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ambiguity between the specified syntax of the Object System and those extensions is
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possible.
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<P>
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<DL COMPACT><DT>``When situation <i>S</i> occurs, an error is signaled.''
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<DD>
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<P>
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This terminology has the following meaning:
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<P>
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<UL><LI> If this situation occurs, an error will be signaled in
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the interpreter and in code compiled under all compiler safety
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optimization levels.
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<P>
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<LI> Valid programs may rely on the fact that an error will be
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signaled in the interpreter and in code compiled under all compiler
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safety optimization levels.
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<P>
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<LI> Every implementation is required to detect such an error
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in the interpreter and in code compiled under all compiler safety
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optimization levels.
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<P>
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</UL>
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<P>
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<DT>``When situation <i>S</i> occurs, an error should be signaled.''
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<DD>
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<P>
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This terminology has the following meaning:
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<P>
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<UL><LI> If this situation occurs, an error will be signaled at
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least in the interpreter and in code compiled under the safest
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compiler safety optimization level.
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<P>
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<LI> Valid programs may not rely on the fact that an error will be
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signaled.
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<P>
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<LI> Every implementation is required to detect such an error
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at least in the interpreter and in code compiled under the safest
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compiler safety optimization level.
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<P>
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<LI> When an error is not signaled, the results are undefined (see
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below).
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<P>
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</UL>
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<P>
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<DT>``When situation <i>S</i> occurs, the results are undefined.''
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<DD>
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<P>
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This terminology has the following meaning:
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<P>
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<UL><LI> If this situation occurs, the results are unpredictable. The
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results may range from harmless to fatal.
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<P>
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<LI> Implementations are allowed to detect this situation and
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signal an error, but no implementation is required to detect the
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situation.
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<P>
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<LI> No valid program may depend on the effects of this
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situation, and all valid programs are required to treat the effects
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of this situation as unpredictable.
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<P>
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</UL>
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<P>
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<DT>``When situation <i>S</i> occurs, the results are unspecified.''
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<DD>
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<P>
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This terminology has the following meaning:
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<P>
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<UL><LI> The effects of this situation are not specified in
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the Object System, but the effects are harmless.
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<P>
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<LI> Implementations are allowed to specify the effects of
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this situation.
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<P>
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<LI> No portable program can depend on the effects of this
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situation, and all portable programs are required to treat the situation
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as unpredictable but harmless.
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<P>
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</UL>
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<P>
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<DT>``The Common Lisp Object System may be extended to cover situation <i>S</i>.''
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<DD>
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<P>
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The meaning of this terminology is that an implementation is free to treat
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situation <i>S</i> in one of three ways:
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<P>
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<UL><LI> When situation <i>S</i> occurs, an error is signaled at least
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in the interpreter and in code compiled under the safest compiler
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safety optimization level.
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<P>
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<LI> When situation <i>S</i> occurs, the results are undefined.
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<P>
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<LI> When situation <i>S</i> occurs, the results are defined and
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specified.
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<P>
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</UL>
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<P>
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In addition, this terminology has the following meaning:
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<P>
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<UL><LI> No portable program can depend on the effects of this
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situation, and all portable programs are required to treat the situation
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as undefined.
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<P>
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</UL>
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<P>
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<DT>``Implementations are free to extend the syntax <i>S</i>.''
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<DD>
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<P>
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This terminology has the following meaning:
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<P>
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<UL><LI> Implementations are allowed to define unambiguous extensions
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to syntax <i>S</i>.
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<P>
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<LI> No portable program can depend on this extension, and
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all portable programs are required to treat the syntax
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as meaningless.
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<P>
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</UL>
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<P>
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</DL>
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<P>
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The Common Lisp Object System specification may disallow certain extensions while allowing others.
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<br><img align=bottom alt="change_end" src="gif/change_end.gif">
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<P>
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<BR> <HR><A NAME=tex2html4934 HREF="node263.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html4932 HREF="node261.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html4926 HREF="node261.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html4936 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html4937 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html4935 HREF="node263.html"> Classes</A>
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|
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<B>Up:</B> <A NAME=tex2html4933 HREF="node261.html"> Programmer Interface Concepts</A>
|
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|
|
<B> Previous:</B> <A NAME=tex2html4927 HREF="node261.html"> Programmer Interface Concepts</A>
|
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|
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<HR> <P>
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|
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<HR>
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<P><ADDRESS>
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AI.Repository@cs.cmu.edu
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</ADDRESS>
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</BODY>
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