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49 lines
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<TITLE>CLHS: Section 25.1.4</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="25_ac.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="25_a.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="25_ada.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<H2>
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25.1.4 Time</H2> <P>
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Time is represented in four different ways in Common Lisp: <A REL=DEFINITION HREF="26_glo_d.htm#decoded_time"><I>decoded time</I></A>, <A REL=DEFINITION HREF="26_glo_u.htm#universal_time"><I>universal time</I></A>, <A REL=DEFINITION HREF="26_glo_i.htm#internal_time"><I>internal time</I></A>, and seconds. <A REL=DEFINITION HREF="26_glo_d.htm#decoded_time"><I>Decoded time</I></A> and <A REL=DEFINITION HREF="26_glo_u.htm#universal_time"><I>universal time</I></A> are used primarily to represent calendar time, and are precise only to one second. <A REL=DEFINITION HREF="26_glo_i.htm#internal_time"><I>Internal time</I></A> is used primarily to represent measurements of computer time (such as run time) and is precise to some <A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A> fraction of a second called an <A REL=DEFINITION HREF="26_glo_i.htm#internal_time_unit"><I>internal time unit</I></A>, as specified by <A REL=DEFINITION HREF="v_intern.htm#internal-time-units-per-second"><B>internal-time-units-per-second</B></A>. An <A REL=DEFINITION HREF="26_glo_i.htm#internal_time"><I>internal time</I></A> can be used for either <A REL=DEFINITION HREF="26_glo_a.htm#absolute"><I>absolute</I></A> and <A REL=DEFINITION HREF="26_glo_r.htm#relative"><I>relative</I></A> <A REL=DEFINITION HREF="26_glo_t.htm#time"><I>time</I></A> measurements. Both a <A REL=DEFINITION HREF="26_glo_u.htm#universal_time"><I>universal time</I></A> and a <A REL=DEFINITION HREF="26_glo_d.htm#decoded_time"><I>decoded time</I></A> can be used only for <A REL=DEFINITION HREF="26_glo_a.htm#absolute"><I>absolute</I></A> <A REL=DEFINITION HREF="26_glo_t.htm#time"><I>time</I></A> measurements. In the case of one function, <A REL=DEFINITION HREF="f_sleep.htm#sleep"><B>sleep</B></A>, time intervals are represented as a non-negative <A REL=DEFINITION HREF="t_real.htm#real"><I>real</I></A> number of seconds. <P>
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The next figure shows <A REL=DEFINITION HREF="26_glo_d.htm#defined_name"><I>defined names</I></A> relating to <A REL=DEFINITION HREF="26_glo_t.htm#time"><I>time</I></A>. <P>
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<PRE>
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<A REL=DEFINITION HREF="f_dec_un.htm#decode-universal-time">decode-universal-time</A> <A REL=DEFINITION HREF="f_get__1.htm#get-internal-run-time">get-internal-run-time</A>
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<A REL=DEFINITION HREF="f_encode.htm#encode-universal-time">encode-universal-time</A> <A REL=DEFINITION HREF="f_get_un.htm#get-universal-time">get-universal-time</A>
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<A REL=DEFINITION HREF="f_get_un.htm#get-decoded-time">get-decoded-time</A> <A REL=DEFINITION HREF="v_intern.htm#internal-time-units-per-second">internal-time-units-per-second</A>
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<A REL=DEFINITION HREF="f_get_in.htm#get-internal-real-time">get-internal-real-time</A> <A REL=DEFINITION HREF="f_sleep.htm#sleep">sleep</A>
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</PRE>
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<P><B>Figure 25-4. Defined names involving Time.</B> <P>
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<A REL=CHILD HREF="25_ada.htm"><H2>
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25.1.4.1 Decoded Time</H2></A><P>
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<A REL=CHILD HREF="25_adb.htm"><H2>
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25.1.4.2 Universal Time</H2></A><P>
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<A REL=CHILD HREF="25_adc.htm"><H2>
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25.1.4.3 Internal Time</H2></A><P>
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<A REL=CHILD HREF="25_add.htm"><H2>
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25.1.4.4 Seconds</H2></A><P><HR>
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