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32 lines
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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 22.3.6.1</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="22_cf.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="22_cf.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="22_cfb.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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22.3.6.1 Tilde T: Tabulate</H2> <P>
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This spaces over to a given column. <TT>~</TT><I>colnum</I><TT>,</TT><I>colinc</I><TT>T</TT> will output sufficient spaces to move the cursor to column <I>colnum</I>. If the cursor is already at or beyond column <I>colnum</I>, it will output spaces to move it to column <I>colnum</I>+<I>k</I>*<I>colinc</I> for the smallest positive integer <I>k</I> possible, unless <I>colinc</I> is zero, in which case no spaces are output if the cursor is already at or beyond column <I>colnum</I>. <I>colnum</I> and <I>colinc</I> default to <TT>1</TT>. <P>
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If for some reason the current absolute column position cannot be determined by direct inquiry, <A REL=DEFINITION HREF="f_format.htm#format"><B>format</B></A> may be able to deduce the current column position by noting that certain directives (such as <TT>~%</TT>, or <TT>~&</TT>, or <TT>~A</TT> with the argument being a string containing a newline) cause the column position to be reset to zero, and counting the number of characters emitted since that point. If that fails, <A REL=DEFINITION HREF="f_format.htm#format"><B>format</B></A> may attempt a similar deduction on the riskier assumption that the destination was at column zero when <A REL=DEFINITION HREF="f_format.htm#format"><B>format</B></A> was invoked. If even this heuristic fails or is implementationally inconvenient, at worst the <TT>~T</TT> operation will simply output two spaces. <P>
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<TT>~@T</TT> performs relative tabulation. <TT>~</TT><I>colrel</I><TT>,</TT><I>colinc</I><TT>@T</TT> outputs <I>colrel</I> spaces and then outputs the smallest non-negative number of additional spaces necessary to move the cursor to a column that is a multiple of <I>colinc</I>. For example, the directive <TT>~3,8@T</TT> outputs three spaces and then moves the cursor to a ``standard multiple-of-eight tab stop'' if not at one already. If the current output column cannot be determined, however, then <I>colinc</I> is ignored, and exactly <I>colrel</I> spaces are output. <P>
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If the <A REL=DEFINITION HREF="26_glo_c.htm#colon"><I>colon</I></A> modifier is used with the <TT>~T</TT> directive, the tabbing computation is done relative to the horizontal position where the section immediately containing the directive begins, rather than with respect to a horizontal position of zero. The numerical parameters are both interpreted as being in units of <A REL=DEFINITION HREF="26_glo_e.htm#em"><I>ems</I></A> and both default to <TT>1</TT>. <TT>~</TT><I>n</I><TT>,</TT><I>m</I><TT>:T</TT> is the same as <TT>(pprint-tab :section </TT><I>n</I><TT> </TT><I>m</I><TT>)</TT>. <TT>~</TT><I>n</I><TT>,</TT><I>m</I><TT>:@T</TT> is the same as <TT>(pprint-tab :section-relative </TT><I>n</I><TT> </TT><I>m</I><TT>)</TT>. <P>
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<A REL=NAVIGATOR HREF="../Front/StartPts.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Starting Points]" SRC="../Graphics/StartPts.gif" ALIGN=Bottom></A><A REL=TOC HREF="../Front/Contents.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Contents]" SRC="../Graphics/Contents.gif" ALIGN=Bottom></A><A REL=INDEX HREF="../Front/X_Master.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Index]" SRC="../Graphics/Index.gif" ALIGN=Bottom></A><A REL=INDEX HREF="../Front/X_Symbol.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Symbols]" SRC="../Graphics/Symbols.gif" ALIGN=Bottom></A><A REL=GLOSSARY HREF="../Body/26_a.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Glossary]" SRC="../Graphics/Glossary.gif" ALIGN=Bottom></A><A HREF="../Front/X3J13Iss.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Issues]" SRC="../Graphics/Issues.gif" ALIGN=Bottom></A><BR>
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<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
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