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<H1> 4.1.2 Slices</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> [<A NAME="I2295"></A> A <FONT FACE="Arial, Helvetica">slice</FONT>
denotes a one-dimensional array formed by a sequence of consecutive components
of a one-dimensional array. A <FONT FACE="Arial, Helvetica">slice</FONT>
of a variable is a variable; a <FONT FACE="Arial, Helvetica">slice</FONT>
of a constant is a constant;] a <FONT FACE="Arial, Helvetica">slice</FONT>
of a value is a value. </DIV>
<H4 ALIGN=CENTER>Syntax</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="SyntaxIndented"><FONT FACE="Arial, Helvetica">slice<A NAME="I2296"></A>
::= </FONT><A NAME="I2297"></A><FONT FACE="Arial, Helvetica">prefix</FONT>(<A NAME="I2298"></A><FONT FACE="Arial, Helvetica">discrete_range</FONT>)</DIV>
<H4 ALIGN=CENTER>Name Resolution Rules</H4>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="Normal"> The <FONT FACE="Arial, Helvetica">prefix</FONT>
of a <FONT FACE="Arial, Helvetica">slice</FONT> shall resolve to denote
a one-dimensional array (after any implicit dereference).</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="Normal"> <A NAME="I2299"></A>The expected type for the
<FONT FACE="Arial, Helvetica">discrete_range</FONT> of a <FONT FACE="Arial, Helvetica">slice</FONT>
is the index type of the array type. </DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Normal"> A <FONT FACE="Arial, Helvetica">slice</FONT> denotes
a one-dimensional array formed by the sequence of consecutive components
of the array denoted by the <FONT FACE="Arial, Helvetica">prefix</FONT>,
corresponding to the range of values of the index given by the <FONT FACE="Arial, Helvetica">discrete_range</FONT>.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Normal"> The type of the <FONT FACE="Arial, Helvetica">slice</FONT>
is that of the <FONT FACE="Arial, Helvetica">prefix</FONT>. Its bounds
are those defined by the <FONT FACE="Arial, Helvetica">discrete_range</FONT>.</DIV>
<H4 ALIGN=CENTER>Dynamic Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Normal"> <A NAME="I2300"></A>For the evaluation of a <FONT FACE="Arial, Helvetica">slice</FONT>,
the <FONT FACE="Arial, Helvetica">prefix</FONT> and the <FONT FACE="Arial, Helvetica">discrete_range</FONT>
are evaluated in an arbitrary order. <A NAME="I2301"></A><A NAME="I2302"></A><A NAME="I2303"></A>If
the <FONT FACE="Arial, Helvetica">slice</FONT> is not a <I>null slice</I>
(a <FONT FACE="Arial, Helvetica">slice</FONT> where the <FONT FACE="Arial, Helvetica">discrete_range</FONT>
is a null range), then a check is made that the bounds of the <FONT FACE="Arial, Helvetica">discrete_range</FONT>
belong to the index range of the array denoted by the <FONT FACE="Arial, Helvetica">prefix</FONT>.
<A NAME="I2304"></A>Constraint_Error is raised if this check fails.</DIV>
<DIV Class="NotesHeader"><FONT SIZE=-1>NOTES</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>2 A <FONT FACE="Arial, Helvetica">slice</FONT>
is not permitted as the <FONT FACE="Arial, Helvetica">prefix</FONT> of
an Access <FONT FACE="Arial, Helvetica">attribute_reference</FONT>, even
if the components or the array as a whole are aliased. See <A HREF="AA-3-10-2.html">3.10.2</A>.
</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Proof: </B>Slices are not aliased,
by <A HREF="AA-3-10.html">3.10</A>, ``<A HREF="AA-3-10.html">Access Types</A>''.
</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B>This is to ease
implementation of general-access-to-array. If slices were aliased, implementations
would need to store array dope with the access values, which is not always
desirable given access-to-incomplete types completed in a package body.
</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>3 For a one-dimensional array
A, the <FONT FACE="Arial, Helvetica">slice</FONT> A(N .. N) denotes an
array that has only one component; its type is the type of A. On the
other hand, A(N) denotes a component of the array A and has the corresponding
component type. </FONT></DIV>
<H4 ALIGN=CENTER>Examples</H4>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> <I>Examples of
slices:</I> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<DIV Class="Examples"><TT> Stars(1 .. 15) <I>-- a slice of 15 characters (see <A HREF="AA-3-6-3.html">3.6.3</A>)</I><BR>
Page(10 .. 10 + Size) <I>-- a slice of 1 + Size components (see <A HREF="AA-3-6.html">3.6</A>)</I><BR>
Page(L)(A .. B) <I>-- a slice of the array Page(L) (see <A HREF="AA-3-6.html">3.6</A>)</I><BR>
Stars(1 .. 0) <I>-- a null slice (see <A HREF="AA-3-6-3.html">3.6.3</A>)</I><BR>
My_Schedule(Weekday) <I>-- bounds given by subtype (see <A HREF="AA-3-6-1.html">3.6.1</A> and <A HREF="AA-3-5-1.html">3.5.1</A>)</I><BR>
Stars(5 .. 15)(K) <I>-- same as Stars(K) (see <A HREF="AA-3-6-3.html">3.6.3</A>)</I><BR>
<I>-- provided that K is in 5 .. 15</I></TT></DIV>
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