355 lines
7 KiB
HTML
355 lines
7 KiB
HTML
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<HTML LANG="en-us"
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>signum | Common Lisp Nova Spec</TITLE
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>Common Lisp Nova Spec</A
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> <SPAN CLASS="breadcrumb-item"
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>signum</A
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>→</A
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></DIV
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><DIV CLASS="matter"
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><DIV CLASS="com"
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><DIV CLASS="begincom"
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><HR
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><TABLE WIDTH="100%" CELLSPACING="0" CELLPADDING="0"
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><TR
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><TD ALIGN="LEFT" VALIGN="BASELINE" WIDTH="100%" CLASS="name"
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><SPAN CLASS="idx" DATA-KIND="idxref" DATA-TERM="signum"
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></SPAN
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><B
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>signum</B
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></TD
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><TD ALIGN="RIGHT" VALIGN="BASELINE" WIDTH="0" NOWRAP="NOWRAP" CLASS="ftype"
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><I
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>Function</I
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></TD
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></TR
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></TABLE
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><HR
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></DIV
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><UL CLASS="subtoc"
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></UL
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><DL
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><DT
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><B
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>Syntax</B
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></DT
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><DD
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><P CLASS="j"
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><B
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>signum</B
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> <SPAN CLASS="cmssi"
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>number</SPAN
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> <SPAN CLASS="arrow"
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>→</SPAN
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> <SPAN CLASS="cmssi"
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>signed-prototype</SPAN
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></P
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></DD
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><DT
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><B
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>Arguments and Values</B
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></DT
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><DD
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><P CLASS="j"
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><VAR CLASS="param"
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>number</VAR
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> — a <A HREF="26_1_Glossary.html#number"
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><EM CLASS="term"
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>number</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>signed-prototype</VAR
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> — a <A HREF="26_1_Glossary.html#number"
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><EM CLASS="term"
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>number</EM
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></A
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>.</P
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></DD
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><DT
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><B
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>Description</B
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></DT
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><DD
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><P CLASS="j"
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><A HREF="f_signum.html" CLASS="funref"
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><B
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>signum</B
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></A
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> determines a numerical value that indicates whether <VAR CLASS="param"
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>number</VAR
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> is negative, zero, or positive. </P
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><P CLASS="j"
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>For a <A HREF="26_1_Glossary.html#rational"
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><EM CLASS="term"
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>rational</EM
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></A
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>, <A HREF="f_signum.html" CLASS="funref"
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><B
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>signum</B
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></A
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> returns one of <CODE CLASS="f"
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>-1</CODE
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>, <CODE CLASS="f"
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>0</CODE
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>, or <CODE CLASS="f"
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>1</CODE
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> according to whether <VAR CLASS="param"
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>number</VAR
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> is negative, zero, or positive. For a <A HREF="26_1_Glossary.html#float"
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><EM CLASS="term"
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>float</EM
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></A
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>, the result is a <A HREF="26_1_Glossary.html#float"
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><EM CLASS="term"
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>float</EM
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></A
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> of the same format whose value is minus one, zero, or one. For a <A HREF="26_1_Glossary.html#complex"
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><EM CLASS="term"
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>complex</EM
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></A
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> number <CODE CLASS="f"
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>z</CODE
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>, <CODE CLASS="f"
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>(signum <I CLASS="i"
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><I
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>z</I
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></I
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>)</CODE
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> is a complex number of the same phase but with unit magnitude, unless <CODE CLASS="f"
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>z</CODE
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> is a complex zero, in which case the result is <CODE CLASS="f"
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>z</CODE
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>. </P
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><P CLASS="j"
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>For <A HREF="26_1_Glossary.html#rational"
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><EM CLASS="term"
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>rational</EM
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></A
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> <A HREF="26_1_Glossary.html#argument"
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><EM CLASS="term"
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>arguments</EM
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></A
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>, <A HREF="f_signum.html" CLASS="funref"
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><B
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>signum</B
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></A
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> is a rational function, but it may be irrational for <A HREF="26_1_Glossary.html#complex"
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><EM CLASS="term"
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>complex</EM
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></A
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> <A HREF="26_1_Glossary.html#argument"
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><EM CLASS="term"
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>arguments</EM
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></A
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>. </P
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><P CLASS="j"
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>If <VAR CLASS="param"
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>number</VAR
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> is a <A HREF="26_1_Glossary.html#float"
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><EM CLASS="term"
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>float</EM
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></A
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>, the result is a <A HREF="26_1_Glossary.html#float"
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><EM CLASS="term"
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>float</EM
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></A
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>. If <VAR CLASS="param"
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>number</VAR
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> is a <A HREF="26_1_Glossary.html#rational"
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><EM CLASS="term"
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>rational</EM
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></A
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>, the result is a <A HREF="26_1_Glossary.html#rational"
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><EM CLASS="term"
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>rational</EM
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></A
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>. If <VAR CLASS="param"
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>number</VAR
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> is a <A HREF="26_1_Glossary.html#complex_float"
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><EM CLASS="term"
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>complex float</EM
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></A
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>, the result is a <A HREF="26_1_Glossary.html#complex_float"
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><EM CLASS="term"
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>complex float</EM
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></A
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>. If <VAR CLASS="param"
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>number</VAR
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> is a <A HREF="26_1_Glossary.html#complex_rational"
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><EM CLASS="term"
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>complex rational</EM
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></A
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>, the result is a <A HREF="26_1_Glossary.html#complex"
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><EM CLASS="term"
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>complex</EM
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></A
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>, but it is <A HREF="26_1_Glossary.html#implementation-dependent"
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><EM CLASS="term"
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>implementation-dependent</EM
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></A
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> whether that result is a <A HREF="26_1_Glossary.html#complex_rational"
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><EM CLASS="term"
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>complex rational</EM
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></A
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> or a <A HREF="26_1_Glossary.html#complex_float"
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><EM CLASS="term"
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>complex float</EM
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></A
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>.</P
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></DD
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><DT
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><B
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>Examples</B
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></DT
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><DD
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><PRE CLASS="screen"
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>(signum 0) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> 0
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(signum 99) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> 1
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(signum 4/5) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> 1
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(signum -99/100) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> -1
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(signum 0.0) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> 0.0
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(signum #c(0 33)) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> #C(0.0 1.0)
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(signum #c(7.5 10.0)) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> #C(0.6 0.8)
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(signum #c(0.0 -14.7)) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> #C(0.0 -1.0)
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(eql (signum -0.0) -0.0) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> <A HREF="26_1_Glossary.html#true"
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><EM CLASS="term"
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>true</EM
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></A
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></PRE
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></DD
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><DT
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><B
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>See Also</B
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></DT
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><DD
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><P CLASS="j"
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><A HREF="12_1_Number_Concepts.html#sec_12_1_3_3" CLASS="secref"
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><SPAN CLASS="cmr"
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>Section</SPAN
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> <SPAN CLASS="cmr"
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>12.1.3.3</SPAN
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> <SPAN CLASS="cmr"
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>(Rule</SPAN
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> <SPAN CLASS="cmr"
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>of</SPAN
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> <SPAN CLASS="cmr"
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>Float</SPAN
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> <SPAN CLASS="cmr"
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>Substitutability)</SPAN
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></A
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></P
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></DD
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><DT
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><B
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>Notes</B
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></DT
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><DD
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><PRE CLASS="screen"
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>(signum x) <SPAN CLASS="cmsy"
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><SPAN STYLE="font-size:16px;vertical-align:-2px"
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>≡</SPAN
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></SPAN
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> (if (zerop x) x (/ x (abs x)))</PRE
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></DD
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></DL
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></DIV
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></DIV
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><DIV CLASS="footer"
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><DIV CLASS="btmnav"
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><A HREF="f_mod.html" CLASS="prev"
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>←</A
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><A HREF="f_sqrt.html" CLASS="next"
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>→</A
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></DIV
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><DIV CLASS="trail"
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>Conversion to HTML copyright 2023 by Gilbert Baumann</DIV
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>domReady();</SCRIPT
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>
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