71 lines
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71 lines
6.6 KiB
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<TITLE>CLHS: Accessor SUBSEQ</TITLE>
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<A NAME="subseq"><I>Accessor</I> <B>SUBSEQ</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>subseq</B> <I>sequence start <TT>&optional</TT> end</I> => <I>subsequence</I><P>
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<TT>(setf (</TT><B>subseq</B> <I>sequence start <TT>&optional</TT> end</I><TT>) </TT><I>new-subsequence</I><TT>)</TT><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>sequence</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#proper_sequence"><I>proper sequence</I></A>. <P>
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<I>start</I>, <I>end</I>---<A REL=DEFINITION HREF="26_glo_b.htm#bounding_index_designator"><I>bounding index designators</I></A> of <I>sequence</I>. The default for <I>end</I> is <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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<I>subsequence</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#proper_sequence"><I>proper sequence</I></A>. <P>
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<I>new-subsequence</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#proper_sequence"><I>proper sequence</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="#subseq"><B>subseq</B></A> creates a <A REL=DEFINITION HREF="26_glo_s.htm#sequence"><I>sequence</I></A> that is a copy of the subsequence of <I>sequence</I> <I>bounded</I> by <I>start</I> and <I>end</I>. <P>
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<I>Start</I> specifies an offset into the original <I>sequence</I> and marks the beginning position of the subsequence. <I>end</I> marks the position following the last element of the subsequence. <P>
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<A REL=DEFINITION HREF="#subseq"><B>subseq</B></A> always allocates a new <A REL=DEFINITION HREF="26_glo_s.htm#sequence"><I>sequence</I></A> for a result; it never shares storage with an old <A REL=DEFINITION HREF="26_glo_s.htm#sequence"><I>sequence</I></A>. The result subsequence is always of the same <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> as <I>sequence</I>. <P>
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If <I>sequence</I> is a <A REL=DEFINITION HREF="26_glo_v.htm#vector"><I>vector</I></A>, the result is a <A REL=DEFINITION HREF="26_glo_f.htm#fresh"><I>fresh</I></A> <A REL=DEFINITION HREF="26_glo_s.htm#simple_array"><I>simple array</I></A> of <A REL=DEFINITION HREF="26_glo_r.htm#rank"><I>rank</I></A> one that has the same <A REL=DEFINITION HREF="26_glo_a.htm#actual_array_element_type"><I>actual array element type</I></A> as <I>sequence</I>. If <I>sequence</I> is a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>, the result is a <A REL=DEFINITION HREF="26_glo_f.htm#fresh"><I>fresh</I></A> <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>. <P>
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<A REL=DEFINITION HREF="m_setf_.htm#setf"><B>setf</B></A> may be used with <A REL=DEFINITION HREF="#subseq"><B>subseq</B></A> to destructively replace <A REL=DEFINITION HREF="26_glo_e.htm#element"><I>elements</I></A> of a subsequence with <A REL=DEFINITION HREF="26_glo_e.htm#element"><I>elements</I></A> taken from a <A REL=DEFINITION HREF="26_glo_s.htm#sequence"><I>sequence</I></A> of new values. If the subsequence and the new sequence are not of equal length, the shorter length determines the number of elements that are replaced. The remaining <A REL=DEFINITION HREF="26_glo_e.htm#element"><I>elements</I></A> at the end of the longer sequence are not modified in the operation. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(setq str "012345") => "012345"
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(subseq str 2) => "2345"
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(subseq str 3 5) => "34"
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(setf (subseq str 4) "abc") => "abc"
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str => "0123ab"
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(setf (subseq str 0 2) "A") => "A"
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str => "A123ab"
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B> None.
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<P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>Exceptional Situations:</B><P>
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<P>
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Should be prepared to signal an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> if <I>sequence</I> is not a <A REL=DEFINITION HREF="26_glo_p.htm#proper_sequence"><I>proper sequence</I></A>. Should be prepared to signal an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> if <I>new-subsequence</I> is not a <A REL=DEFINITION HREF="26_glo_p.htm#proper_sequence"><I>proper sequence</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_replac.htm#replace"><B>replace</B></A> <P>
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<P><B>Notes:</B> None.
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<P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issues</A>, <I>not part of the specification</I>, apply to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss284.htm">RANGE-OF-START-AND-END-PARAMETERS:INTEGER-AND-INTEGER-NIL</A><LI> <A REL=CHILD HREF="../Issues/iss332.htm">SUBSEQ-OUT-OF-BOUNDS</A><P></UL><HR>
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