59 lines
4.4 KiB
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59 lines
4.4 KiB
HTML
<!-- 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: Variable +, ++, +++</TITLE>
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<A NAME="PL"><A NAME="PLPL"><A NAME="PLPLPL"><I>Variable</I> <B>+, ++, +++</B></A></A></A> <P>
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<P><B>Value Type:</B><P>
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<P>
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an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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<P><B>Initial Value:</B><P>
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<P>
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<A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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The <A REL=DEFINITION HREF="26_glo_v.htm#variable"><I>variables</I></A> <A REL=DEFINITION HREF="#PL"><B>+</B></A>, <A REL=DEFINITION HREF="#PLPL"><B>++</B></A>, and <A REL=DEFINITION HREF="#PLPLPL"><B>+++</B></A> are maintained by the <A REL=DEFINITION HREF="26_glo_l.htm#lisp_read-eval-print_loop"><I>Lisp read-eval-print loop</I></A> to save <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>forms</I></A> that were recently <I>evaluated</I>. <P>
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The <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A> of <A REL=DEFINITION HREF="a_pl.htm#PL"><B>+</B></A> is the last <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> that was <I>evaluated</I>, the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A> of <A REL=DEFINITION HREF="#PLPL"><B>++</B></A> is the previous value of <A REL=DEFINITION HREF="a_pl.htm#PL"><B>+</B></A>, and the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A> of <A REL=DEFINITION HREF="#PLPLPL"><B>+++</B></A> is the previous value of <A REL=DEFINITION HREF="#PLPL"><B>++</B></A>. <P>
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<P><B>Examples:</B><P>
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<PRE>
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(+ 0 1) => 1
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(- 4 2) => 2
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(/ 9 3) => 3
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(list + ++ +++) => ((/ 9 3) (- 4 2) (+ 0 1))
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(setq a 1 b 2 c 3 d (list a b c)) => (1 2 3)
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(setq a 4 b 5 c 6 d (list a b c)) => (4 5 6)
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(list a b c) => (4 5 6)
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(eval +++) => (1 2 3)
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#.`(,@++ d) => (1 2 3 (1 2 3))
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</PRE>
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</TT> <P>
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<P><B>Affected By:</B><P>
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<P>
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<A REL=DEFINITION HREF="26_glo_l.htm#lisp_read-eval-print_loop"><I>Lisp read-eval-print loop</I></A>. <P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="f__.htm#-"><B>-</B></A> (<A REL=DEFINITION HREF="26_glo_v.htm#variable"><I>variable</I></A>), <A REL=DEFINITION HREF="f_st.htm#ST"><B>*</B></A> (<A REL=DEFINITION HREF="26_glo_v.htm#variable"><I>variable</I></A>), <A REL=DEFINITION HREF="f_sl.htm#SL"><B>/</B></A> (<A REL=DEFINITION HREF="26_glo_v.htm#variable"><I>variable</I></A>), <A REL=CHILD HREF="25_aa.htm">Section 25.1.1 (Top level loop)</A> <P>
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<P><B>Notes:</B> None.
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<P>
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