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<H1> 8.4 Use Clauses</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> A <FONT FACE="Arial, Helvetica">use_package_clause</FONT>
achieves direct visibility of declarations that appear in the visible
part of a package; a <FONT FACE="Arial, Helvetica">use_type_clause</FONT>
achieves direct visibility of the primitive operators of a type. </DIV>
<H4 ALIGN=CENTER>Syntax</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="SyntaxIndented"><FONT FACE="Arial, Helvetica">use_clause<A NAME="I3223"></A>
::= </FONT><A NAME="I3224"></A><FONT FACE="Arial, Helvetica">use_package_clause</FONT> | <A NAME="I3225"></A><FONT FACE="Arial, Helvetica">use_type_clause</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="SyntaxIndented"><FONT FACE="Arial, Helvetica">use_package_clause<A NAME="I3226"></A>
::= </FONT><B>use</B> <I>package_</I><A NAME="I3227"></A><FONT FACE="Arial, Helvetica">name</FONT> {, <I>package_</I><A NAME="I3228"></A><FONT FACE="Arial, Helvetica">name</FONT>};</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="SyntaxIndented"><FONT FACE="Arial, Helvetica">use_type_clause<A NAME="I3229"></A>
::= </FONT><B>use type</B> <A NAME="I3230"></A><FONT FACE="Arial, Helvetica">subtype_mark</FONT> {, <A NAME="I3231"></A><FONT FACE="Arial, Helvetica">subtype_mark</FONT>};</DIV>
<H4 ALIGN=CENTER>Legality Rules</H4>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Normal"> A <I>package_</I><FONT FACE="Arial, Helvetica">name</FONT>
of a <FONT FACE="Arial, Helvetica">use_package_clause</FONT> shall denote
a package. </DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3232"></A>For each <FONT FACE="Arial, Helvetica">use_clause</FONT>,
there is a certain region of text called the <I>scope</I> of the <FONT FACE="Arial, Helvetica">use_clause</FONT>.
For a <FONT FACE="Arial, Helvetica">use_clause</FONT> within a <FONT FACE="Arial, Helvetica">context_clause</FONT>
of a <FONT FACE="Arial, Helvetica">library_unit_declaration</FONT> or
<FONT FACE="Arial, Helvetica">library_unit_renaming_declaration</FONT>,
the scope is the entire declarative region of the declaration. For a
<FONT FACE="Arial, Helvetica">use_clause</FONT> within a <FONT FACE="Arial, Helvetica">context_clause</FONT>
of a body, the scope is the entire body and any subunits (including multiply
nested subunits). The scope does not include <FONT FACE="Arial, Helvetica">context_clause</FONT>s
themselves.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Normal"> For a <FONT FACE="Arial, Helvetica">use_clause</FONT>
immediately within a declarative region, the scope is the portion of
the declarative region starting just after the <FONT FACE="Arial, Helvetica">use_clause</FONT>
and extending to the end of the declarative region. However, the scope
of a <FONT FACE="Arial, Helvetica">use_clause</FONT> in the private part
of a library unit does not include the visible part of any public descendant
of that library unit. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3233"></A>For each package denoted by
a <I>package_</I><FONT FACE="Arial, Helvetica">name</FONT> of a <FONT FACE="Arial, Helvetica">use_package_clause</FONT>
whose scope encloses a place, each declaration that occurs immediately
within the declarative region of the package is <I>potentially</I> <I>use-visible</I>
at this place if the declaration is visible at this place. For each type
<I>T</I> or <I>T</I>'Class determined by a <FONT FACE="Arial, Helvetica">subtype_mark</FONT>
of a <FONT FACE="Arial, Helvetica">use_type_clause</FONT> whose scope
encloses a place, the declaration of each primitive operator of type
<I>T</I> is potentially use-visible at this place if its declaration
is visible at this place. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> <A NAME="I3234"></A><A NAME="I3235"></A>A
declaration is <I>use-visible</I> if it is potentially use-visible, except
in these naming-conflict cases: </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>A potentially use-visible declaration is not use-visible
if the place considered is within the immediate scope of a homograph
of the declaration.</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>Potentially use-visible declarations that have the same
<FONT FACE="Arial, Helvetica">identifier</FONT> are not use-visible unless
each of them is an overloadable declaration. </LI></UL>
<H4 ALIGN=CENTER>Dynamic Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>12</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3236"></A>The elaboration of a <FONT FACE="Arial, Helvetica">use_clause</FONT>
has no effect. </DIV>
<H4 ALIGN=CENTER>Examples</H4>
<DIV Class="Paranum"><FONT SIZE=-2>13</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> <I>Example of a
use clause in a context clause:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>14</FONT></DIV>
<DIV Class="Examples"><TT><B>with</B> Ada.Calendar; <B>use</B> Ada;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>15</FONT></DIV>
<DIV Class="Wide" Style="margin-bottom: 0.4em"> <I>Example of a use
type clause:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16</FONT></DIV>
<DIV Class="Examples"><TT><B>use type</B> Rational_Numbers.Rational; --<I> see <A HREF="RM-7-1.html">7.1</A></I><BR>
Two_Thirds: Rational_Numbers.Rational := 2/3;</TT></DIV>
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