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typo fixed and em-dash used instead of a single hypen for parenthetical phrases.

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[SVN r17923]
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Fernando Cacciola
2003-03-14 20:40:08 +00:00
parent 0267424bfe
commit 7d8ab81d48
1 changed files with 10 additions and 11 deletions
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@ -191,15 +191,15 @@ bool operator != ( optional<T> const& lhs, optional<T> const&amp
<P>This meaning of the null pointer value allowed pointers to became a defacto standard <P>This meaning of the null pointer value allowed pointers to became a defacto standard
for handling optional objects because all you have to do to refer to a value which you for handling optional objects because all you have to do to refer to a value which you
don't really have is to use a null pointer value of the appropriate type. don't really have is to use a null pointer value of the appropriate type.
Pointers have been used for decades -from the days of C APIs to modern C++ libraries- Pointers have been used for decades&mdash;from the days of C APIs to modern C++ libraries&mdash;to
to <i>refer</i> to optional (that is, possibly inexistent) objects; particularly <i>refer</i> to optional (that is, possibly inexistent) objects; particularly
as optional arguments to a function, but also quite often as optional data members.</P> as optional arguments to a function, but also quite often as optional data members.</P>
<P>The possible presence of a null pointer value makes the operations that access the <P>The possible presence of a null pointer value makes the operations that access the
pointee's value possibly undefined, therefore, expressions which use dereference pointee's value possibly undefined, therefore, expressions which use dereference
and access operators, such as: <code>( *p = 2 )</code> and <code>( p-&gt;foo())</code>, and access operators, such as: <code>( *p = 2 )</code> and <code>( p-&gt;foo())</code>,
implicitly convey the notion of optionality, and this information is tied to implicitly convey the notion of optionality, and this information is tied to
the <i>syntax</i> of the expressions. That is, the presence of operators * and -&gt; tell by the <i>syntax</i> of the expressions. That is, the presence of operators * and -&gt; tell by
themselves -without any additional context-, that the expression will be undefined unless themselves&mdash;without any additional context&mdash;that the expression will be undefined unless
the implied pointee actually exist.<br> the implied pointee actually exist.<br>
Furthermore, the existence of the pointee can be tested by a comparison against Furthermore, the existence of the pointee can be tested by a comparison against
the null pointer value or via a conversion to bool, which allows expressions of the null pointer value or via a conversion to bool, which allows expressions of
@ -228,7 +228,7 @@ them. The problem resides in the shallow-copy of pointer semantics: if you need
possible undefined value because of the idiomatic aid present in the OptionalPointee possible undefined value because of the idiomatic aid present in the OptionalPointee
concept incarnated by pointers. <br> concept incarnated by pointers. <br>
Therefore, the final solution which is presented in this library is to shape the Therefore, the final solution which is presented in this library is to shape the
previously discussed optional -which is a value-based container- as a model previously discussed optional&mdash;which is a value-based container&mdash;as a model
of the OptionalPointee concept. of the OptionalPointee concept.
</p> </p>
<h3>Optional&lt;T&gt; as a model of OptionalPointee</h3> <h3>Optional&lt;T&gt; as a model of OptionalPointee</h3>
@ -806,14 +806,13 @@ class Fred
<H2><A NAME="bool">A note about optional&lt;bool&gt;</A></H2> <H2><A NAME="bool">A note about optional&lt;bool&gt;</A></H2>
<p><code>optional&lt;bool&gt;</code> should be used with special caution and consideration.</p> <p><code>optional&lt;bool&gt;</code> should be used with special caution and consideration.</p>
<p>First, it is functionally similar to a tristate boolean (false,maybe,true) <p>First, it is functionally similar to a tristate boolean (false,maybe,true) &mdash;such as
-such as <u>boost::tribool</u> (not yet formally in boost)-, <u>boost::tribool</u> (not yet formally in boost)&mdash;except that in a tristate boolean,
except that in a tristate boolean, the <i>maybe</i> state the <i>maybe</i> state <u>represents a valid value</u>, unlike the corresponding state
<u>represents a valid value</u>, unlike the corresponding state
of an uninitialized optional&lt;bool&gt;.<br> of an uninitialized optional&lt;bool&gt;.<br>
It should be carefully considered if an optional bool instead of a tribool is really needed</p> It should be carefully considered if an optional bool instead of a tribool is really needed</p>
<p>Second, optional&lt;&gt; provides and implicit conversion to bool. This conversion <p>Second, optional&lt;&gt; provides an implicit conversion to bool. This conversion
refers to the initialization state and not to the contained value.<br> refers to the initialization state and not to the contained value.<br>
Using optional&lt;bool&gt; can lead to subtle errors due to the implicit bool conversion:</p> Using optional&lt;bool&gt; can lead to subtle errors due to the implicit bool conversion:</p>
<pre> <pre>
void foo ( bool v ) ; void foo ( bool v ) ;
@ -978,6 +977,6 @@ HREF="http://www.boost.org">www.boost.org</A>, and the boost discussion list at
<A <A
HREF="http://www.yahoogroups.com/list/boost">www.yahoogroups.com/list/boost</A>. HREF="http://www.yahoogroups.com/list/boost">www.yahoogroups.com/list/boost</A>.
</P> </P>
</u></BODY> </BODY>
</HTML> </HTML>