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<H1> 12.2 Generic Bodies</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I4184"></A>The body of a generic unit
(a <I>generic body</I>) [is a template for the instance bodies. The syntax
of a generic body is identical to that of a nongeneric body]. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>We also use
terms like ``generic function body'' and ``nongeneric package body.''
</FONT></DIV>
<H4 ALIGN=CENTER>Dynamic Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal"> <A NAME="I4185"></A>The elaboration of a generic
body has no other effect than to establish that the generic unit can
from then on be instantiated without failing the Elaboration_Check. If
the generic body is a child of a generic package, then its elaboration
establishes that each corresponding declaration nested in an instance
of the parent (see <A HREF="AA-10-1-1.html">10.1.1</A>) can from then
on be instantiated without failing the Elaboration_Check. </DIV>
<DIV Class="NotesHeader"><FONT SIZE=-1>NOTES</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>4 The syntax of generic subprograms
implies that a generic subprogram body is always the completion of a
declaration. </FONT></DIV>
<H4 ALIGN=CENTER>Examples</H4>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> <I>Example of a
generic procedure body:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Examples"><TT><B>procedure</B> Exchange(U, V : <B>in</B> <B>out</B> Elem) <B>is</B> --<I> see <A HREF="AA-12-1.html">12.1</A></I><BR>
T : Elem; --<I> the generic formal type</I><BR>
<B>begin</B><BR>
T := U;<BR>
U := V;<BR>
V := T;<BR>
<B>end</B> Exchange;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Wide" Style="margin-bottom: 0.4em"> <I>Example of a generic
function body:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Squaring(X : Item) <B>return</B> Item <B>is</B> --<I> see <A HREF="AA-12-1.html">12.1</A></I><BR>
<B>begin</B><BR>
<B>return</B> X*X; --<I> the formal operator "*"</I><BR>
<B>end</B> Squaring;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Wide" Style="margin-bottom: 0.4em"> <I>Example of a generic
package body:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Examples"><TT><B>package</B> <B>body</B> On_Vectors <B>is</B> --<I> see <A HREF="AA-12-1.html">12.1</A></I></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> Sum(A, B : Vector) <B>return</B> Vector <B>is</B><BR>
Result : Vector(A'Range); --<I> the formal type Vector</I><BR>
Bias : <B>constant</B> Integer := B'First - A'First;<BR>
<B>begin</B><BR>
<B>if</B> A'Length /= B'Length <B>then</B><BR>
<B>raise</B> Length_Error;<BR>
<B>end</B> <B>if</B>;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<DIV Class="Examples"><TT> <B>for</B> N <B>in</B> A'Range <B>loop</B><BR>
Result(N) := Sum(A(N), B(N + Bias)); --<I> the formal function Sum</I><BR>
<B>end</B> <B>loop</B>;<BR>
<B>return</B> Result;<BR>
<B>end</B> Sum;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>12</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> Sigma(A : Vector) <B>return</B> Item <B>is</B><BR>
Total : Item := A(A'First); --<I> the formal type Item</I><BR>
<B>begin</B><BR>
<B>for</B> N <B>in</B> A'First + 1 .. A'Last <B>loop</B><BR>
Total := Sum(Total, A(N)); --<I> the formal function Sum</I><BR>
<B>end</B> <B>loop</B>;<BR>
<B>return</B> Total;<BR>
<B>end</B> Sigma;<BR>
<B>end</B> On_Vectors;</TT></DIV>
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