/usr/lib/swi-prolog/doc/Manual/help.html

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<TITLE>SWI-Prolog 5.11.18 Reference Manual: Section 2.6</TITLE><LINK REL=home HREF="index.html">
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<H2><A NAME="sec:2.6"><SPAN class="sec-nr">2.6</SPAN> <SPAN class="sec-title">Online 
Help</SPAN></A></H2>

<A NAME="sec:help"></A>

<P>Online help provides a fast lookup and browsing facility to this 
manual. The online manual can show predicate definitions as well as 
entire sections of the manual.

<P>The online help is displayed from the file <CODE>library('MANUAL')</CODE>. 
The file
<CODE>library(helpidx)</CODE> provides an index into this file. <CODE>library('MANUAL')</CODE> 
is created from the LaTeX sources with a modified version of
<B>dvitty</B>, using overstrike for printing bold text and underlining 
for rendering italic text. XPCE is shipped with
<CODE>library(swi_help)</CODE>, presenting the information from the 
online help in a hypertext window. The Prolog flag <A class="flag" href="flags.html#flag:write_help_with_overstrike">write_help_with_overstrike</A> 
controls whether or not <A NAME="idx:help1:80"></A><A class="pred" href="help.html#help/1">help/1</A> 
writes its output using overstrike to realise bold and underlined output 
or not. If this Prolog flag is not set it is initialised by the help 
library to <CODE>true</CODE> if the <CODE>TERM</CODE> variable equals <CODE>xterm</CODE> 
and <CODE>false</CODE> otherwise. If this default does not satisfy you, 
add the following line to your personal startup file (see <A class="sec" href="initfile.html">section 
2.2</A>):

<PRE class="code">
:- set_prolog_flag(write_help_with_overstrike, true).
</PRE>

<DL class="latex">
<DT class="pubdef"><A NAME="help/0"><STRONG>help</STRONG></A></DT>
<DD class="defbody">
Equivalent to <CODE>help(<A NAME="idx:help1:81"></A><A class="pred" href="help.html#help/1">help/1</A>)</CODE>.</DD>
<DT class="pubdef"><A NAME="help/1"><STRONG>help</STRONG>(<VAR>+What</VAR>)</A></DT>
<DD class="defbody">
Show specified part of the manual. <VAR>What</VAR> is one of:
<CENTER>
<TABLE BORDER=0 FRAME=void RULES=groups>
<TR VALIGN=top><TD>&lt;<VAR>Name</VAR>&gt;/&lt;<VAR>Arity</VAR>&gt; </TD><TD>Give 
help on specified predicate </TD></TR>
<TR VALIGN=top><TD>&lt;<VAR>Name</VAR>&gt; </TD><TD>Give help on named 
predicate with any arity or C interface function with that name </TD></TR>
<TR VALIGN=top><TD>&lt;<VAR>Section</VAR>&gt; </TD><TD>Display specified 
section. Section numbers are dash-separated numbers: <CODE>2-3</CODE> 
refers to section 2.3 of the manual. Section numbers are obtained using <A NAME="idx:apropos1:82"></A><A class="pred" href="help.html#apropos/1">apropos/1</A>.</TD></TR>
</TABLE>

</CENTER>

<P>Examples:
<CENTER>
<TABLE BORDER=0 FRAME=void RULES=groups>
<TR VALIGN=top><TD><CODE>?- help(assert).</CODE> </TD><TD>Give help on 
predicate assert </TD></TR>
<TR VALIGN=top><TD><CODE>?- help(3-4).</CODE> </TD><TD>Display section 
3.4 of the manual </TD></TR>
<TR VALIGN=top><TD><CODE>?- help('PL_retry').</CODE></TD><TD>Give help 
on interface function <A class="func" href="foreigninclude.html#PL_retry()">PL_retry()</A> </TD></TR>
</TABLE>

</CENTER>

<P>See also <A NAME="idx:apropos1:83"></A><A class="pred" href="help.html#apropos/1">apropos/1</A>, 
and the SWI-Prolog home page at
<A class="url" href="http://www.swi-prolog.org">http://www.swi-prolog.org</A>, 
which provides a FAQ, an HTML version of manual for online browsing and 
HTML and PDF versions for downloading.</DD>
<DT class="pubdef"><A NAME="apropos/1"><STRONG>apropos</STRONG>(<VAR>+Pattern</VAR>)</A></DT>
<DD class="defbody">
Display all predicates, functions and sections that have <EM>Pattern</EM> 
in their name or summary description. Lowercase letters in
<VAR>Pattern</VAR> also match a corresponding uppercase letter. Example:
<CENTER>
<TABLE BORDER=0 FRAME=void RULES=groups>
<TR VALIGN=top><TD><CODE>?- apropos(file).</CODE> </TD><TD>Display 
predicates, functions and sections that have `file' (or `File', etc.) in 
their summary description. </TD></TR>
</TABLE>

</CENTER>
</DD>
<DT class="pubdef"><A NAME="explain/1"><STRONG>explain</STRONG>(<VAR>+ToExplain</VAR>)</A></DT>
<DD class="defbody">
Give an explanation on the given `object'. The argument may be any 
Prolog data object. If the argument is an atom, a term of the form
<VAR>Name/Arity</VAR> or a term of the form <EM>Module:Name/Arity</EM>,
<A NAME="idx:explain1:84"></A><A class="pred" href="help.html#explain/1">explain/1</A> 
describes the predicate as well as possible references to it. See also <A NAME="idx:gxref0:85"></A><A class="pred" href="xref.html#gxref/0">gxref/0</A>.</DD>
<DT class="pubdef"><A NAME="explain/2"><STRONG>explain</STRONG>(<VAR>+ToExplain, 
-Explanation</VAR>)</A></DT>
<DD class="defbody">
Unify <VAR>Explanation</VAR> with an explanation for <VAR>ToExplain</VAR>. 
Backtracking yields further explanations.
</DD>
</DL>

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swi-prolog-nox 5.10.4-3ubuntu1 / usr / lib / swi-prolog / doc / Manual / help.html
