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<H2><A NAME="sec:5.9"><SPAN class="sec-nr">5.9</SPAN> <SPAN class="sec-title">Module 
Handling Predicates</SPAN></A></H2>

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

<P>This section gives the predicate definitions for the remaining 
built-in predicates that handle modules.

<DL>
<DT class="pubdef"><A NAME="module/2">:- <STRONG>module</STRONG>(<VAR>+Module, +PublicList</VAR>)</A></DT>
<DD class="defbody">
This directive can only be used as the first term of a source file. It 
declares the file to be a <EM>module file</EM>, defining <VAR>Module</VAR> 
and exporting the predicates of <VAR>PublicList</VAR>. <VAR>PublicList</VAR> 
is a list of predicate indicators (name/arity or name//arity pairs) or 
operator declarations using the format <CODE>op(Precedence, Type, Name)</CODE>. 
Operators defined in the export list are available inside the module as 
well as to modules importing this module. See also
<A class="sec" href="operators.html">section 4.24</A>.</DD>
<DT class="pubdef"><A NAME="module_transparent/1"><STRONG>module_transparent</STRONG> <VAR>+Preds</VAR></A></DT>
<DD class="defbody">
<VAR>Preds</VAR> is a comma separated list of name/arity pairs (like
<A NAME="idx:dynamic1:1176"></A><A class="pred" href="dynamic.html#dynamic/1">dynamic/1</A>). 
Each goal associated with a transparent declared predicate will inherit 
the <EM>context module</EM> from its parent goal.</DD>
<DT class="pubdef"><A NAME="meta_predicate/1"><STRONG>meta_predicate</STRONG> <VAR>+Heads</VAR></A></DT>
<DD class="defbody">
This predicate is defined in <CODE>library(quintus)</CODE> and provides 
a partial emulation of the Quintus predicate. See <A class="sec" href="modulecompat.html">section 
5.10.1</A> for details.</DD>
<DT class="pubdef"><A NAME="current_module/1"><STRONG>current_module</STRONG>(<VAR>-Module</VAR>)</A></DT>
<DD class="defbody">
Generates all currently known modules.</DD>
<DT class="pubdef"><A NAME="current_module/2"><STRONG>current_module</STRONG>(<VAR>?Module, 
?File</VAR>)</A></DT>
<DD class="defbody">
Is true if <VAR>File</VAR> is the file from which <VAR>Module</VAR> was 
loaded.
<VAR>File</VAR> is the internal canonical filename. See also
<A NAME="idx:sourcefile12:1177"></A><A class="pred" href="consulting.html#source_file/1">source_file/[1,2]</A>.</DD>
<DT class="pubdef"><A NAME="context_module/1"><STRONG>context_module</STRONG>(<VAR>-Module</VAR>)</A></DT>
<DD class="defbody">
Unify <VAR>Module</VAR> with the context module of the current goal.
<A NAME="idx:contextmodule1:1178"></A><A class="pred" href="manipmodule.html#context_module/1">context_module/1</A> 
itself is transparent.</DD>
<DT class="pubdef"><A NAME="strip_module/3"><STRONG>strip_module</STRONG>(<VAR>+Term, 
-Module, -Plain</VAR>)</A></DT>
<DD class="defbody">
Used in module transparent or meta-predicates to extract the referenced 
module and plain term. If <VAR>Term</VAR> is a module-qualified term, 
i.e. of the format <VAR>Module</VAR>:<VAR>Plain</VAR>, <VAR>Module</VAR> 
and <VAR>Plain</VAR> are unified to these values. Otherwise <VAR>Plain</VAR> 
is unified to
<VAR>Term</VAR> and <VAR>Module</VAR> to the context module.</DD>
<DT class="pubdef"><A NAME="export/1"><STRONG>export</STRONG>(<VAR>+PredicateIndicator, 
...</VAR>)</A></DT>
<DD class="defbody">
Add a predicate to the public list of the context module. This implies 
the predicate will be imported into another module if this module is 
imported with <A NAME="idx:usemodule12:1179"></A><A class="pred" href="import.html#use_module/1">use_module/[1,2]</A>. 
Note that predicates are normally exported using the directive <A NAME="idx:module2:1180"></A><A class="pred" href="manipmodule.html#module/2">module/2</A>. <A NAME="idx:export1:1181"></A><A class="pred" href="manipmodule.html#export/1">export/1</A> 
is meant to handle export from dynamically created modules.</DD>
<DT class="pubdef"><A NAME="export_list/2"><STRONG>export_list</STRONG>(<VAR>+Module, 
?Exports</VAR>)</A></DT>
<DD class="defbody">
Unifies <VAR>Exports</VAR> with a list of predicate indicators, one for 
each public predicate of <VAR>Module</VAR>. The order of the terms in
<VAR>Exports</VAR> is not defined. Predicate indicators are in canonical 
form (i.e. always using Name/Arity and never the DCG form Name//Arity). 
Future versions may also use the DCG form and include public operators. 
See also <A NAME="idx:predicateproperty2:1182"></A><A class="pred" href="examineprog.html#predicate_property/2">predicate_property/2</A>.</DD>
<DT class="pubdef"><A NAME="import_module/2"><STRONG>import_module</STRONG>(<VAR>+Module, 
-Import</VAR>)</A></DT>
<DD class="defbody">
True if <VAR>Import</VAR> is defined as an import module for <VAR>Module</VAR>. 
All normal modules only import from <CODE>user</CODE>, which imports 
from
<CODE>system</CODE>. The predicates <A NAME="idx:addimportmodule3:1183"></A><A class="pred" href="manipmodule.html#add_import_module/3">add_import_module/3</A> 
and
<A NAME="idx:deleteimportmodule2:1184"></A><A class="pred" href="manipmodule.html#delete_import_module/2">delete_import_module/2</A> 
can be used to manipulate the import list.</DD>
<DT class="pubdef"><A NAME="add_import_module/3"><STRONG>add_import_module</STRONG>(<VAR>+Module, 
+Import, +StartOrEnd</VAR>)</A></DT>
<DD class="defbody">
If <VAR>Import</VAR> is not already an import module for <VAR>Module</VAR>, 
add it to this list at the <CODE>start</CODE> or <CODE>end</CODE> 
depending on
<VAR>StartOrEnd</VAR>. See also <A NAME="idx:importmodule2:1185"></A><A class="pred" href="manipmodule.html#import_module/2">import_module/2</A> 
and <A NAME="idx:deleteimportmodule2:1186"></A><A class="pred" href="manipmodule.html#delete_import_module/2">delete_import_module/2</A>.</DD>
<DT class="pubdef"><A NAME="delete_import_module/2"><STRONG>delete_import_module</STRONG>(<VAR>+Module, 
+Import</VAR>)</A></DT>
<DD class="defbody">
Delete <VAR>Import</VAR> from the list of import modules for <VAR>Module</VAR>. 
Fails silently if <VAR>Import</VAR> is not in the list.</DD>
<DT class="pubdef"><A NAME="default_module/2"><STRONG>default_module</STRONG>(<VAR>+Module, 
-Default</VAR>)</A></DT>
<DD class="defbody">
Successively unifies <VAR>Default</VAR> with the module names from which 
a call in <VAR>Module</VAR> attempts to use the definition. For the 
module <CODE>user</CODE>, this will generate <CODE>user</CODE> and <CODE>system</CODE>. 
For any other module, this will generate the module itself, followed by <CODE>user</CODE> 
and <CODE>system</CODE>.

<P>Backward compatibility. New code should use <A NAME="idx:importmodule2:1187"></A><A class="pred" href="manipmodule.html#import_module/2">import_module/2</A>.</DD>
<DT class="pubdef"><A NAME="module/1"><STRONG>module</STRONG>(<VAR>+Module</VAR>)</A></DT>
<DD class="defbody">
The call <CODE>module(<VAR>Module</VAR>)</CODE> may be used to switch 
the default working module for the interactive top-level (see <A NAME="idx:prolog0:1188"></A><A class="pred" href="toplevel.html#prolog/0">prolog/0</A>). 
This may be used to when debugging a module. The example below lists the 
clauses of file_of_label/2 in the module <CODE>tex</CODE>.

<PRE class="code">
1 ?- module(tex).

Yes
tex: 2 ?- listing(file_of_label/2).
...
</PRE>

<P></DD>
</DL>

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