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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: Section 12.1.4.1</TITLE>
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<H2>
12.1.4.1 Rule of Float and Rational Contagion</H2> <P>
When <A REL=DEFINITION HREF="26_glo_r.htm#rational"><I>rationals</I></A> and <A REL=DEFINITION HREF="26_glo_f.htm#float"><I>floats</I></A> are combined by a numerical function, the <A REL=DEFINITION HREF="26_glo_r.htm#rational"><I>rational</I></A> is first converted to a <A REL=DEFINITION HREF="26_glo_f.htm#float"><I>float</I></A> of the same format. For <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>functions</I></A> such as <A REL=DEFINITION HREF="f_pl.htm#PL"><B>+</B></A> that take more than two arguments, it is permitted that part of the operation be carried out exactly using <A REL=DEFINITION HREF="26_glo_r.htm#rational"><I>rationals</I></A> and the rest be done using floating-point arithmetic. <P>
When <A REL=DEFINITION HREF="26_glo_r.htm#rational"><I>rationals</I></A> and <A REL=DEFINITION HREF="26_glo_f.htm#float"><I>floats</I></A> are compared by a numerical function, the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="f_ration.htm#rational"><B>rational</B></A> is effectively called to convert the <A REL=DEFINITION HREF="26_glo_f.htm#float"><I>float</I></A> to a <A REL=DEFINITION HREF="26_glo_r.htm#rational"><I>rational</I></A> and then an exact comparison is performed. In the case of <A REL=DEFINITION HREF="26_glo_c.htm#complex"><I>complex</I></A> numbers, the real and imaginary parts are effectively handled individually. <P>
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12.1.4.1.1 Examples of Rule of Float and Rational Contagion</H2></A><P> <P>
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