61 lines
4.2 KiB
HTML
61 lines
4.2 KiB
HTML
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<TITLE>CLHS: Variable *READ-BASE*</TITLE>
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<A NAME="STread-baseST"><I>Variable</I> <B>*READ-BASE*</B></A> <P>
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<P><B>Value Type:</B><P>
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<P>
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a <A REL=DEFINITION HREF="26_glo_r.htm#radix"><I>radix</I></A>. <P>
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<P><B>Initial Value:</B><P>
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<P>
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<TT>10</TT>. <P>
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<P><B>Description:</B><P>
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<P>
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Controls the interpretation of tokens by <A REL=DEFINITION HREF="f_rd_rd.htm#read"><B>read</B></A> as being <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integers</I></A> or <A REL=DEFINITION HREF="26_glo_r.htm#ratio"><I>ratios</I></A>. <P>
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The <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A> of <A REL=DEFINITION HREF="#STread-baseST"><B>*read-base*</B></A>, called the <A REL=DEFINITION HREF="26_glo_c.htm#current_input_base"><I>current input base</I></A>, is the radix in which <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integers</I></A> and <A REL=DEFINITION HREF="26_glo_r.htm#ratio"><I>ratios</I></A> are to be read by the <A REL=DEFINITION HREF="26_glo_l.htm#lisp_reader"><I>Lisp reader</I></A>. The parsing of other numeric <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>types</I></A> (e.g., <A REL=DEFINITION HREF="26_glo_f.htm#float"><I>floats</I></A>) is not affected by this option. <P>
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The effect of <A REL=DEFINITION HREF="#STread-baseST"><B>*read-base*</B></A> on the reading of any particular <A REL=DEFINITION HREF="26_glo_r.htm#rational"><I>rational</I></A> number can be locally overridden by explicit use of the <TT>#O</TT>, <TT>#X</TT>, <TT>#B</TT>, or <TT>#</TT><I>n</I><TT>R</TT> syntax or by a trailing decimal point. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(dotimes (i 6)
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(let ((*read-base* (+ 10. i)))
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(let ((object (read-from-string "(\\DAD DAD |BEE| BEE 123. 123)")))
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(print (list *read-base* object)))))
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>> (10 (DAD DAD BEE BEE 123 123))
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>> (11 (DAD DAD BEE BEE 123 146))
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>> (12 (DAD DAD BEE BEE 123 171))
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>> (13 (DAD DAD BEE BEE 123 198))
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>> (14 (DAD 2701 BEE BEE 123 227))
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>> (15 (DAD 3088 BEE 2699 123 258))
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=> NIL
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</PRE>
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</TT> <P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>See Also:</B> None.
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<P>
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<P><B>Notes:</B><P>
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<P>
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Altering the input radix can be useful when reading data files in special formats. <P>
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