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<H1> 3.2.1 Type Declarations</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> A <FONT FACE="Arial, Helvetica">type_declaration</FONT>
declares a type and its first subtype. </DIV>
<H4 ALIGN=CENTER>Syntax</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="SyntaxIndented"><FONT FACE="Arial, Helvetica">type_declaration<A NAME="I1364"></A>
::= </FONT> <A NAME="I1365"></A><FONT FACE="Arial, Helvetica">full_type_declaration</FONT><BR>
| <A NAME="I1366"></A><FONT FACE="Arial, Helvetica">incomplete_type_declaration</FONT><BR>
| <A NAME="I1367"></A><FONT FACE="Arial, Helvetica">private_type_declaration</FONT><BR>
| <A NAME="I1368"></A><FONT FACE="Arial, Helvetica">private_extension_declaration</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="SyntaxIndented"><FONT FACE="Arial, Helvetica">full_type_declaration<A NAME="I1369"></A>
::= </FONT><BR>
<B>type</B> <A NAME="I1370"></A><FONT FACE="Arial, Helvetica">defining_identifier</FONT> [<A NAME="I1371"></A><FONT FACE="Arial, Helvetica">known_discriminant_part</FONT>] <B>is</B> <A NAME="I1372"></A><FONT FACE="Arial, Helvetica">type_definition</FONT>;<BR>
| <A NAME="I1373"></A><FONT FACE="Arial, Helvetica">task_type_declaration</FONT><BR>
| <A NAME="I1374"></A><FONT FACE="Arial, Helvetica">protected_type_declaration</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="SyntaxIndented"><FONT FACE="Arial, Helvetica">type_definition<A NAME="I1375"></A>
::= </FONT><BR>
<A NAME="I1376"></A><FONT FACE="Arial, Helvetica">enumeration_type_definition</FONT> | <A NAME="I1377"></A><FONT FACE="Arial, Helvetica">integer_type_definition</FONT><BR>
| <A NAME="I1378"></A><FONT FACE="Arial, Helvetica">real_type_definition</FONT> | <A NAME="I1379"></A><FONT FACE="Arial, Helvetica">array_type_definition</FONT><BR>
| <A NAME="I1380"></A><FONT FACE="Arial, Helvetica">record_type_definition</FONT> | <A NAME="I1381"></A><FONT FACE="Arial, Helvetica">access_type_definition</FONT><BR>
| <A NAME="I1382"></A><FONT FACE="Arial, Helvetica">derived_type_definition</FONT></DIV>
<H4 ALIGN=CENTER>Legality Rules</H4>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Normal"> A given type shall not have a subcomponent whose
type is the given type itself. </DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1383"></A>The <FONT FACE="Arial, Helvetica">defining_identifier</FONT>
of a <FONT FACE="Arial, Helvetica">type_declaration</FONT> denotes the
<I>first subtype</I> of the type. The <FONT FACE="Arial, Helvetica">known_discriminant_part</FONT>,
if any, defines the discriminants of the type (see <A HREF="AA-3-7.html">3.7</A>,
``<A HREF="AA-3-7.html">Discriminants</A>''). The remainder of the <FONT FACE="Arial, Helvetica">type_declaration</FONT>
defines the remaining characteristics of (the view of) the type.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1384"></A>A type defined by a <FONT FACE="Arial, Helvetica">type_declaration</FONT>
is a <I>named</I> type; such a type has one or more nameable subtypes.
<A NAME="I1385"></A>Certain other forms of declaration also include type
definitions as part of the declaration for an object (including a parameter
or a discriminant). The type defined by such a declaration is <I>anonymous</I>
-- it has no nameable subtypes. <A NAME="I1386"></A>For explanatory purposes,
this International Standard sometimes refers to an anonymous type by
a pseudo-name, written in italics, and uses such pseudo-names at places
where the syntax normally requires an <FONT FACE="Arial, Helvetica">identifier</FONT>.
For a named type whose first subtype is T, this International Standard
sometimes refers to the type of T as simply ``the type T.'' </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>The only
user-defined types that can be anonymous in the above sense are array,
access, task, and protected types. An anonymous array, task, or protected
type can be defined as part of an <FONT FACE="Arial, Helvetica">object_declaration</FONT>.
An anonymous access type can be defined as part of a parameter or discriminant
specification. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1387"></A>A named type that is declared
by a <FONT FACE="Arial, Helvetica">full_type_declaration</FONT>, or an
anonymous type that is defined as part of declaring an object of the
type, is called a <I>full type</I>. <A NAME="I1388"></A>The <FONT FACE="Arial, Helvetica">type_definition</FONT>,
<FONT FACE="Arial, Helvetica">task_definition</FONT>, <FONT FACE="Arial, Helvetica">protected_definition</FONT>,
or <FONT FACE="Arial, Helvetica">access_definition</FONT> that defines
a full type is called a <I>full type definition</I>. [Types declared
by other forms of <FONT FACE="Arial, Helvetica">type_declaration</FONT>
are not separate types; they are partial or incomplete views of some
full type.] </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>To be honest: </B>Class-wide,
universal, and root numeric types are full types. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1389"></A>The definition of a type implicitly
declares certain <I>predefined operators</I> that operate on the type,
according to what classes the type belongs, as specified in <A HREF="AA-4-5.html">4.5</A>,
``<A HREF="AA-4-5.html">Operators and Expression Evaluation</A>''. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Discussion: </B>We no longer
talk about the implicit declaration of basic operations. These are treated
like an <FONT FACE="Arial, Helvetica">if_statement</FONT> -- they don't
need to be declared, but are still applicable to only certain classes
of types.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1390"></A>The <I>predefined types</I>
[(for example the types Boolean, Wide_Character, Integer, <I>root_integer</I>,
and <I>universal_integer</I>)] are the types that are defined in [a predefined
library package called] Standard[; this package also includes the [(implicit)]
declarations of their predefined operators]. [The package Standard is
described in <A HREF="AA-A-1.html">A.1</A>.] </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>We use the
term ``predefined'' to refer to entities declared in the visible part
of Standard, to implicitly declared operators of a type whose semantics
are defined by the language, to Standard itself, and to the ``predefined
environment''. We do not use this term to refer to library packages other
than Standard. For example Text_IO is a language-defined package, not
a predefined package, and Text_IO.Put_Line is not a predefined operation.
</FONT></DIV>
<H4 ALIGN=CENTER>Dynamic Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<DIV Class="Normal"> <A NAME="I1391"></A>The elaboration of a <FONT FACE="Arial, Helvetica">full_type_declaration</FONT>
consists of the elaboration of the full type definition. <A NAME="I1392"></A>Each
elaboration of a full type definition creates a distinct type and its
first subtype. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B>The creation is
associated with the type <I>definition</I>, rather than the type <I>declaration</I>,
because there are types that are created by full type definitions that
are not immediately contained within a type declaration (e.g. an array
object declaration, a singleton task declaration, etc.). </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>Any implicit
declarations that occur immediately following the full type definition
are elaborated where they (implicitly) occur. </FONT></DIV>
<H4 ALIGN=CENTER>Examples</H4>
<DIV Class="Paranum"><FONT SIZE=-2>12</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> <I>Examples of
type definitions:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>13</FONT></DIV>
<DIV Class="Examples"><TT>(White, Red, Yellow, Green, Blue, Brown, Black)<BR>
<B>range</B> 1 .. 72<BR>
<B>array</B>(1 .. 10) <B>of</B> Integer</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>14</FONT></DIV>
<DIV Class="Wide" Style="margin-bottom: 0.4em"> <I>Examples of type
declarations:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>15</FONT></DIV>
<DIV Class="Examples"><TT><B>type</B> Color <B>is</B> (White, Red, Yellow, Green, Blue, Brown, Black);<BR>
<B>type</B> Column <B>is</B> <B>range</B> 1 .. 72;<BR>
<B>type</B> Table <B>is</B> <B>array</B>(1 .. 10) <B>of</B> Integer;</TT></DIV>
<DIV Class="NotesHeader"><FONT SIZE=-1>NOTES</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>3 Each of the above examples
declares a named type. The identifier given denotes the first subtype
of the type. Other named subtypes of the type can be declared with <FONT FACE="Arial, Helvetica">subtype_declaration</FONT>s
(see <A HREF="AA-3-2-2.html">3.2.2</A>). Although names do not directly
denote types, a phrase like ``the type Column'' is sometimes used in
this International Standard to refer to the type of Column, where Column
denotes the first subtype of the type. For an example of the definition
of an anonymous type, see the declaration of the array Color_Table in
<A HREF="AA-3-3-1.html">3.3.1</A>; its type is anonymous -- it has no
nameable subtypes. </FONT></DIV>
<H4 ALIGN=CENTER>Wording Changes from Ada 83</H4>
<DIV Class="Paranum"><FONT SIZE=-2>16.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>The syntactic category <FONT FACE="Arial, Helvetica">full_type_declaration</FONT>
now includes task and protected type declarations.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>We have generalized the concept
of first-named subtype (now called simply ``first subtype'') to cover
all kinds of types, for uniformity of description elsewhere. RM83 defined
first-named subtype in Section 13. We define first subtype here, because
it is now a more fundamental concept. We renamed the term, because in
Ada 95 some first subtypes have no name.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>We no longer elaborate <FONT FACE="Arial, Helvetica">discriminant_part</FONT>s,
because there is nothing to do, and it was complex to say that you only
wanted to elaborate it once for a private or incomplete type. This is
also consistent with the fact that subprogram specifications are not
elaborated (neither in Ada 83 nor in Ada 95). Note, however, that an
<FONT FACE="Arial, Helvetica">access_definition</FONT> appearing in a
<FONT FACE="Arial, Helvetica">discriminant_part</FONT> is elaborated
when an object with such a discriminant is created. </FONT></DIV>
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