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Document improved variadic template support

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William S Fulton 2022-12-22 19:35:20 +00:00
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@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
Version 4.2.0 (in progress)
===========================
2022-12-22: wsfulton
Complete support for C++11 variadic templates. Support was previously limited
to just one template parameter. Now zero or more template parameters are supported.
2022-12-06: wsfulton
#1636 Fix syntax error for misplaced Doxygen comment after struct/class member.
Fix syntax error using Doxygen member groups syntax, "///*}", when used after

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@ -1125,38 +1125,71 @@ union P {
<H3><a name="CPlusPlus11_variadic_templates">7.2.18 Variadic templates</a></H3>
<p>SWIG supports the variadic templates syntax (inside the &lt;&gt;
block, variadic class inheritance and variadic constructor and
initializers) with some limitations. The following code is correctly parsed:</p>
<p>SWIG supports the variadic templates including the &lt;&gt;
variadic class inheritance, variadic methods, variadic constructors and
initializers. Example:</p>
<div class="code"><pre>
template &lt;typename... BaseClasses&gt; class ClassName : public BaseClasses... {
public:
ClassName(BaseClasses &amp;&amp;... baseClasses) : BaseClasses(baseClasses)... {}
void InstanceMethod(const BaseClasses&amp;... baseClasses) {}
};
</pre></div>
<p>
For now however, the <tt>%template</tt> directive only accepts one parameter substitution
for the variable template parameters.
The <tt>%template</tt> directive works as expected for variable template parameters.
</p>
<div class="code"><pre>
%template(MyVariant1) ClassName&lt;&gt; // zero argument not supported yet
%template(MyVariant2) ClassName&lt;int&gt; // ok
%template(MyVariant3) ClassName&lt;int, int&gt; // too many arguments not supported yet
struct A {
virtual void amethod();
virtual ~A();
};
struct B {
virtual void bmethod();
virtual ~B();
};
%template(ClassName0) ClassName&lt;&gt;
%template(ClassName1) ClassName&lt;A&gt;
%template(ClassName2) ClassName&lt;A, B&gt;
</pre></div>
<p>Support for the variadic <tt>sizeof()</tt> function is correctly parsed:</p>
<p>
Example usage from say Python:
</p>
<div class="targetlang"><pre>
cn0 = ClassName0()
cn0.InstanceMethod()
a = A()
cn1 = ClassName1(a)
cn1.amethod()
cn1.InstanceMethod(a)
b = B()
cn2 = ClassName2(a, b)
cn2.InstanceMethod(a, b)
cn2.amethod()
cn2.bmethod()
</pre></div>
<p>Support for the variadic <tt>sizeof()</tt> function also works:</p>
<div class="code"><pre>
const int SIZE = sizeof...(ClassName&lt;int, int&gt;);
const int SIZE = sizeof...(ClassName&lt;A, B&gt;);
</pre></div>
<p>
In the above example <tt>SIZE</tt> is of course wrapped as a constant.
</p>
<p>
<b>Compatibility note:</b> SWIG-4.2.0 was the first version to fully support variadic templates.
SWIG-3.0.0 provided initial support and was limited to only one variadic parameter.
</p>
<H3><a name="CPlusPlus11_new_char_literals">7.2.19 New character literals</a></H3>