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<H1> 3.2.3 Classification of Operations</H1>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1419"></A>An operation <I>operates on
a type</I> <I>T</I> if it yields a value of type <I>T</I>, if it has
an operand whose expected type (see <A HREF="AA-8-6.html">8.6</A>) is
<I>T</I>, or if it has an access parameter (see <A HREF="AA-6-1.html">6.1</A>)
designating <I>T</I>. <A NAME="I1420"></A>A predefined operator, or other
language-defined operation such as assignment or a membership test, that
operates on a type, is called a <I>predefined operation</I> of the type.
<A NAME="I1421"></A>The <I>primitive operations</I> of a type are the
predefined operations of the type, plus any user-defined primitive subprograms.
</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Glossary entry: </B>The primitive
operations of a type are the operations (such as subprograms) declared
together with the type declaration. They are inherited by other types
in the same class of types. For a tagged type, the primitive subprograms
are dispatching subprograms, providing run-time polymorphism. A dispatching
subprogram may be called with statically tagged operands, in which case
the subprogram body invoked is determined at compile time. Alternatively,
a dispatching subprogram may be called using a dispatching call, in which
case the subprogram body invoked is determined at run time.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>To be honest: </B>Protected
subprograms are not considered to be ``primitive subprograms,'' even
though they are subprograms, and they are inherited by derived types.
</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Discussion: </B>We use the
term ``primitive subprogram'' in most of the rest of the manual. The
term ``primitive operation'' is used mostly in conceptual discussions.
</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> <A NAME="I1422"></A>The
<I>primitive subprograms</I> of a specific type are defined as follows:
</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>The predefined operators of the type (see <A HREF="AA-4-5.html">4.5</A>);</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>For a derived type, the inherited (see <A HREF="AA-3-4.html">3.4</A>)
user-defined subprograms;</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>For an enumeration type, the enumeration literals (which
are considered parameterless functions -- see <A HREF="AA-3-5-1.html">3.5.1</A>);</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>For a specific type declared immediately within a <FONT FACE="Arial, Helvetica">package_specification</FONT>,
any subprograms (in addition to the enumeration literals) that are explicitly
declared immediately within the same <FONT FACE="Arial, Helvetica">package_specification</FONT>
and that operate on the type;</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC><A NAME="I1423"></A>Any subprograms not covered above [that
are explicitly declared immediately within the same declarative region
as the type] and that override (see <A HREF="AA-8-3.html">8.3</A>) other
implicitly declared primitive subprograms of the type. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>7.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Discussion: </B>In Ada 83,
only subprograms declared in the visible part were ``primitive'' (i.e.
derivable). In Ada 95, mostly because of child library units, we include
all operations declared in the private part as well, and all operations
that override implicit declarations. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>It is possible
for a subprogram to be primitive for more than one type, though it is
illegal for a subprogram to be primitive for more than one tagged type.
See <A HREF="AA-3-9.html">3.9</A>. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Discussion: </B>The order of
the implicit declarations when there are both predefined operators and
inherited subprograms is described in <A HREF="AA-3-4.html">3.4</A>,
``<A HREF="AA-3-4.html">Derived Types and Classes</A>''. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1424"></A>A primitive subprogram whose
designator is an <FONT FACE="Arial, Helvetica">operator_symbol</FONT>
is called a <I>primitive operator</I>.</DIV>
<H4 ALIGN=CENTER>Incompatibilities With Ada 83</H4>
<DIV Class="Paranum"><FONT SIZE=-2>8.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><A NAME="I1425"></A>The attribute
S'Base is no longer defined for non-scalar subtypes. Since this was only
permitted as the prefix of another attribute, and there are no interesting
non-scalar attributes defined for an unconstrained composite or access
subtype, this should not affect any existing programs. </FONT></DIV>
<H4 ALIGN=CENTER>Extensions to Ada 83</H4>
<DIV Class="Paranum"><FONT SIZE=-2>8.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><A NAME="I1426"></A>The primitive
subprograms (derivable subprograms) include subprograms declared in the
private part of a package specification as well, and those that override
implicitly declared subprograms, even if declared in a body. </FONT></DIV>
<H4 ALIGN=CENTER>Wording Changes from Ada 83</H4>
<DIV Class="Paranum"><FONT SIZE=-2>8.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>We have dropped the confusing
term <I>operation of a type</I> in favor of the more useful <I>primitive
operation of a type</I> and the phrase <I>operates on a type</I>.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.d</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>The description of S'Base has
been moved to <A HREF="AA-3-5.html">3.5</A>, ``<A HREF="AA-3-5.html">Scalar
Types</A>'' because it is now defined only for scalar types. </FONT></DIV>
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