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C++11 conversion operator example and docs added

This commit is contained in:
William S Fulton 2014-03-10 19:19:52 +00:00
parent adc3cfeb57
commit 9a45a09aec
2 changed files with 27 additions and 7 deletions
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21
Doc/Manual/CPlusPlus11.html
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@ -517,7 +517,7 @@ class Color {
};
</pre></div>
<p>A workaround is to write these as a series of separated classes containing anonymous enums:</p>
<p>A workaround is to write these as a series of separate classes containing anonymous enums:</p>
<div class="code"><pre>
class PrintingColors {
@ -557,7 +557,7 @@ std::vector&lt;std::vector&lt;int&gt;&gt; myIntTable;
<H3><a name="CPlusPlus11_explicit_conversion_operators"></a>7.2.14 Explicit conversion operators</H3>
<p>SWIG correctly parses the keyword <tt>explicit</tt> both for operators and constructors.
<p>SWIG correctly parses the keyword <tt>explicit</tt> for operators in addition to constructors now.
For example:</p>
<div class="code"><pre>
@ -575,19 +575,26 @@ class TestClass {
public:
//implicit converting constructor
TestClass(U const &amp;val) { t=val.u; }
// explicit constructor
explicit TestClass(V const &amp;val) { t=val.v; }
int t;
};
struct Testable {
// explicit conversion operator
explicit operator bool() const {
return false;
}
};
</pre></div>
<p>
The usage of explicit constructors and operators is somehow specific to C++ when assigning the value
of one object to another one of different type or translating one type to another. It requires both operator and function overloading features,
which are not supported by the majority of SWIG target languages. Also the constructors and operators are not particulary useful in any
SWIG target languages, because all use their own facilities (eg. classes Cloneable and Comparable in Java)
to achieve particular copy and compare behaviours.
The effect of explicit constructors and operators has little relevance for the proxy classes as target
languages don't have the same concepts of implicit conversions as C++.
Conversion operators either with or without <tt>explicit</tt> need renaming to a valid identifier name in order to make
them available as a normal proxy method.
</p>
<H3><a name="CPlusPlus11_alias_templates"></a>7.2.15 Alias templates</H3>

13
Examples/test-suite/cpp11_explicit_conversion_operators.i
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@ -3,6 +3,9 @@
*/
%module cpp11_explicit_conversion_operators
%warnfilter(SWIGWARN_LANG_IDENTIFIER) Testable::operator bool;
%rename(AsInteger) Testable::operator int;
%inline %{
class U {
@ -24,5 +27,15 @@ public:
int t;
};
struct Testable {
// explicit conversion operator
explicit operator bool() const {
return false;
}
explicit operator int() {
return 42;
}
};
%}