Update of /cvsroot/nice/Nice/web
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv10377/web
Modified Files:
manual.xml
Log Message:
Added a section explaining the absence of class casting in Nice.
Index: manual.xml
===================================================================
RCS file: /cvsroot/nice/Nice/web/manual.xml,v
retrieving revision 1.39
retrieving revision 1.40
diff -C2 -d -r1.39 -r1.40
*** manual.xml 2 Sep 2004 16:48:58 -0000 1.39
--- manual.xml 16 Sep 2004 14:21:27 -0000 1.40
***************
*** 16,19 ****
--- 16,20 ----
<author><firstname>Daniel</firstname><surname>Bonniot</surname></author>
<author><firstname>Bryn</firstname><surname>Keller</surname></author>
+ <author><firstname>Francis></firstname><surname>Barber</surname></author>
<copyright><year>2003</year><holder>Daniel Bonniot</holder></copyright>
</bookinfo>
***************
*** 1950,1953 ****
--- 1951,1991 ----
</para>
</section>
+
+ <section id="classCasting"><title>Class Casting</title>
+ <para>
+ Class casting is not used in Nice. Similar to <link
+ linkend="optionTypes">Option types</link> and nullness, if the compiler
+ can prove that the type of an object is compatible with the target
+ context, it will allow that object to be used. This can be done using
+ the <literal>instanceof</literal> operator and an <literal>if</literal>
+ statement:
+ </para>
+ <example>
+ <title>Title</title>
+ <programlisting lang="nice">
+ void foo(FileOutputStream arg) {...}
+
+ void bar(OutputStream arg) {
+ if (arg instanceof FileOutputStream) {
+ //Here Nice knows arg is a FileOutputStream, so it can
+ // be passed to a method which takes a FileOutputStream.
+ foo(arg);
+ }
+ foo(arg); //Here arg may or may not be a FileOutputStream,
+ //so Nice gives a compilation error.
+ }
+ </programlisting>
+ </example>
+ <para>
+ As with <link linkend="optionTypes">Option types</link>, type inference
+ doesn't work on fields of objects or on method calls, only on local
+ variables. There's a good reason for this: the value of an instance
+ variable may have changed (updated by another thread, perhaps) between
+ the time the value was checked for its type and the time it is actually
+ used. Similarly, method calls can return objects of different sub-types
+ every time they are called. To avoid this problem, simply assign the
+ value to a local variable first.
+ </para>
+ </section>
<section id = "typeParameters"><title>Type Parameters</title>
***************
*** 2199,2201 ****
sgml-validate-command: "xmllint -noout -valid"
End:
! -->
--- 2237,2239 ----
sgml-validate-command: "xmllint -noout -valid"
End:
! -->
\ No newline at end of file
|
