93 lines
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93 lines
7.2 KiB
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<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Function WARN</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="f_smp_cn.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_condit.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="e_smp_wa.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="warn"><I>Function</I> <B>WARN</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>warn</B> <I>datum <TT>&rest</TT> arguments</I> => <I><A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A></I><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>datum</I>, <I>arguments</I>---<A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designators</I></A> for a <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> of default type <A REL=DEFINITION HREF="e_smp_wa.htm#simple-warning"><B>simple-warning</B></A>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="26_glo_s.htm#signal"><I>Signals</I></A> a <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_warnin.htm#warning"><B>warning</B></A>. If the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is not <I>handled</I>, reports the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> to <A REL=DEFINITION HREF="26_glo_e.htm#error_output"><I>error output</I></A>. <P>
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The precise mechanism for warning is as follows: <P>
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<P>
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<P><DL><P>
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<DT><B>The warning condition is signaled</B> <P><DD>
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While the <A REL=DEFINITION HREF="e_warnin.htm#warning"><B>warning</B></A> <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is being signaled, the <A REL=DEFINITION HREF="a_muffle.htm#muffle-warning"><B>muffle-warning</B></A> <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> is established for use by a <A REL=DEFINITION HREF="26_glo_h.htm#handler"><I>handler</I></A>. If invoked, this <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> bypasses further action by <A REL=DEFINITION HREF="#warn"><B>warn</B></A>, which in turn causes <A REL=DEFINITION HREF="#warn"><B>warn</B></A> to immediately return <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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<DT><B>If no handler for the warning condition is found</B> <P><DD>
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If no handlers for the warning condition are found, or if all such handlers decline, then the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is reported to <A REL=DEFINITION HREF="26_glo_e.htm#error_output"><I>error output</I></A> by <A REL=DEFINITION HREF="#warn"><B>warn</B></A> in an <A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A> format. <P>
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<DT><B><A REL=DEFINITION HREF="a_nil.htm#nil">nil</A> is returned</B> <P><DD>
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The value returned by <A REL=DEFINITION HREF="#warn"><B>warn</B></A> if it returns is <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P></DL><P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(defun foo (x)
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(let ((result (* x 2)))
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(if (not (typep result 'fixnum))
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(warn "You're using very big numbers."))
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result))
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=> FOO
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(foo 3)
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=> 6
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(foo most-positive-fixnum)
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>> Warning: You're using very big numbers.
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=> 4294967294
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(setq *break-on-signals* t)
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=> T
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(foo most-positive-fixnum)
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>> Break: Caveat emptor.
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>> To continue, type :CONTINUE followed by an option number.
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>> 1: Return from Break.
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>> 2: Abort to Lisp Toplevel.
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>> Debug> :continue 1
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>> Warning: You're using very big numbers.
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=> 4294967294
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B><P>
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<P>
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A warning is issued. The debugger might be entered. <P>
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<P><B>Affected By:</B><P>
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<P>
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Existing handler bindings. <P>
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<A REL=DEFINITION HREF="v_break_.htm#STbreak-on-signalsST"><B>*break-on-signals*</B></A>, <A REL=DEFINITION HREF="v_debug_.htm#STerror-outputST"><B>*error-output*</B></A>. <P>
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<P><B>Exceptional Situations:</B><P>
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<P>
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If <I>datum</I> is a <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> and if the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is not of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_warnin.htm#warning"><B>warning</B></A>, or <I>arguments</I> is <A REL=DEFINITION HREF="26_glo_n.htm#non-nil"><I>non-nil</I></A>, an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> is signaled. <P>
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If <I>datum</I> is a condition type, the result of <TT>(apply #'make-condition datum arguments)</TT> must be of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_warnin.htm#warning"><B>warning</B></A> or an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> is signaled. <P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="v_break_.htm#STbreak-on-signalsST"><B>*break-on-signals*</B></A>, <A REL=DEFINITION HREF="f_abortc.htm#muffle-warning"><B>muffle-warning</B></A>, <A REL=DEFINITION HREF="f_signal.htm#signal"><B>signal</B></A> <P>
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<P><B>Notes:</B> None.
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<P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issue</A>, <I>not part of the specification</I>, applies to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss020.htm">BREAK-ON-WARNINGS-OBSOLETE:REMOVE</A><P></UL><HR>
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