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/**
\page doc_script_class_ops Operator overloads
It is possible to define what should be done when an operator is
used with a script class. While not necessary in most scripts it can
be useful to improve readability of the code.
This is called operator overloading, and is done by implementing
specific class methods. The compiler will recognize and use these
methods when it compiles expressions involving the overloaded operators
and the script class.
\section doc_script_class_unary_ops Prefixed unary operators
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=80><b>op</b></td><td width=120><b>opfunc</b></td></tr>
<tr><td>-</td> <td>opNeg</td></tr>
<tr><td>~</td> <td>opCom</td></tr>
<tr><td>++</td> <td>opPreInc</td></tr>
<tr><td>\--</td> <td>opPreDec</td></tr>
</table>
When the expression <tt><i>op</i> a</tt> is compiled, the compiler will rewrite it as <tt>a.<i>opfunc</i>()</tt> and compile that instead.
\section doc_script_class_unary2_ops Postfixed unary operators
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=80><b>op</b></td><td width=120><b>opfunc</b></td></tr>
<tr><td>++</td> <td>opPostInc</td></tr>
<tr><td>\--</td> <td>opPostDec</td></tr>
</table>
When the expression <tt>a <i>op</i></tt> is compiled, the compiler will rewrite it as <tt>a.<i>opfunc</i>()</tt> and compile that instead.
\section doc_script_class_cmp_ops Comparison operators
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=80><b>op</b></td><td width=120><b>opfunc</b></td></tr>
<tr><td>==</td> <td>opEquals</td></tr>
<tr><td>!=</td> <td>opEquals</td></tr>
<tr><td><</td> <td>opCmp</td> </tr>
<tr><td><=</td> <td>opCmp</td> </tr>
<tr><td>></td> <td>opCmp</td> </tr>
<tr><td>>=</td> <td>opCmp</td> </tr>
<tr><td>is</td> <td>opEquals</td></tr>
<tr><td>!is</td> <td>opEquals</td></tr>
</table>
The <tt>a == b</tt> expression will be rewritten as <tt>a.opEquals(b)</tt> and <tt>b.opEquals(a)</tt> and
then the best match will be used. <tt>!=</tt> is treated similarly, except that the result is negated. The
opEquals method must be implemented to return a <tt>bool</tt> in order to be considered by the compiler.
The comparison operators are rewritten as <tt>a.opCmp(b) <i>op</i> 0</tt> and <tt>0 <i>op</i> b.opCmp(a)</tt>
and then the best match is used. The opCmp method must be implemented to return a <tt>int</tt> in order to be
considered by the compiler. If the method argument is to be considered larger than the object then the method
should return a negative value. If they are supposed to be equal the return value should be 0.
If an equality check is made and the opEquals method is not available the compiler looks for the opCmp method
instead. So if the opCmp method is available it is really not necesary to implement the opEquals method, except
for optimization reasons.
The identity operator, <tt>is</tt>, expects opEquals to take a handle, <tt>\@</tt>, so the addresses can be
compared to be able to return if it is the same object, in contrast two different objects that have
the same value.
\section doc_script_class_assign_ops Assignment operators
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=80><b>op</b></td><td width=120><b>opfunc</b></td></tr>
<tr><td>=</td> <td>opAssign</td> </tr>
<tr><td>+=</td> <td>opAddAssign</td> </tr>
<tr><td>-=</td> <td>opSubAssign</td> </tr>
<tr><td>*=</td> <td>opMulAssign</td> </tr>
<tr><td>/=</td> <td>opDivAssign</td> </tr>
<tr><td>\%=</td> <td>opModAssign</td> </tr>
<tr><td>**=</td> <td>opPowAssign</td> </tr>
<tr><td>&=</td> <td>opAndAssign</td> </tr>
<tr><td>|=</td> <td>opOrAssign</td> </tr>
<tr><td>^=</td> <td>opXorAssign</td> </tr>
<tr><td><<=</td> <td>opShlAssign</td> </tr>
<tr><td>>>=</td> <td>opShrAssign</td> </tr>
<tr><td>>>>=</td> <td>opUShrAssign</td></tr>
</table>
The assignment expressions <tt>a <i>op</i> b</tt> are rewritten as <tt>a.<i>opfunc</i>(b)</tt> and then the
best matching method is used. An assignment operator can for example be implemented like this:
<pre>
obj@ opAssign(const obj &in other)
{
// Do the proper assignment
...
// Return a handle to self, so that multiple assignments can be chained
return this;
}
</pre>
All script classes have a default assignment operator that does a bitwise copy of the content of the class,
so if that is all you want to do, then there is no need to implement this method.
\section doc_script_class_binary_ops Binary operators
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=80><b>op</b></td><td width=120><b>opfunc</b></td><td><b>opfunc_r</b></td></tr>
<tr><td>+</td> <td>opAdd</td> <td>opAdd_r</td></tr>
<tr><td>-</td> <td>opSub</td> <td>opSub_r</td></tr>
<tr><td>*</td> <td>opMul</td> <td>opMul_r</td></tr>
<tr><td>/</td> <td>opDiv</td> <td>opDiv_r</td></tr>
<tr><td>%</td> <td>opMod</td> <td>opMod_r</td></tr>
<tr><td>**</td> <td>opPow</td> <td>opPow_r</td></tr>
<tr><td>&</td> <td>opAnd</td> <td>opAnd_r</td></tr>
<tr><td>|</td> <td>opOr</td> <td>opOr_r</td></tr>
<tr><td>^</td> <td>opXor</td> <td>opXor_r</td></tr>
<tr><td><<</td> <td>opShl</td> <td>opShl_r</td></tr>
<tr><td>>></td> <td>opShr</td> <td>opShr_r</td></tr>
<tr><td>>>></td> <td>opUShr</td> <td>opUShr_r</td></tr>
</table>
The expressions with binary operators <tt>a <i>op</i> b</tt> will be rewritten as <tt>a.<i>opfunc</i>(b)</tt>
and <tt>b.<i>opfunc_r</i>(a)</tt> and then the best match will be used.
\section doc_script_class_index_op Index operators
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=80><b>op</b></td><td width=120><b>opfunc</b></td></tr>
<tr><td>[]</td> <td>opIndex</td></tr>
</table>
When the expression <tt>a[i]</tt> is compiled, the compiler will rewrite it as <tt>a.opIndex(i)</tt> and compile that instead.
Multiple arguments between the brackets is also supported.
The index operator can also be formed similarly to \ref doc_script_class_prop "property accessors". The get accessor should then be
named <tt>get_opIndex</tt> and have one parameter for the indexing. The set accessor should be named <tt>set_opIndex</tt> and have two
parameters, the first is for the indexing, and the second for the new value.
<pre>
class MyObj
{
float get_opIndex(int idx) const { return 0; }
void set_opIndex(int idx, float value) { }
}
</pre>
When the expression <tt>a[i]</tt> is used to retrieve the value, the compiler will rewrite it as <tt>a.get_opIndex(i)</tt>. When
the expression is used to set the value, the compiler will rewrite it as <tt>a.set_opIndex(i, expr)</tt>.
\section doc_script_class_call Functor operator
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=80><b>op</b></td><td width=120><b>opfunc</b></td></tr>
<tr><td>()</td> <td>opCall</td></tr>
</table>
When the expression <tt>expr(arglist)</tt> is compiled and expr evaluates to an object, the compiler will rewrite it
as <tt>expr.opCall(arglist)</tt> and compile that instead.
\section doc_script_class_conv Type conversion operators
<table cellspacing=0 cellpadding=0 border=0>
<tr><td width=150><b>op</b></td><td width=300><b>opfunc</b></td></tr>
<tr><td><i>type</i>(<i>expr</i>)</td><td><i>constructor</i>, opConv, opImplConv</td></tr>
<tr><td>cast<<i>type</i>>(<i>expr</i>)</td><td>opCast, opImplCast</td></tr>
</table>
When the expression <tt>type(expr)</tt> is compiled and type doesn't have a \ref doc_script_class_construct "conversion constructor" that take an argument with
the type of the expression, the compiler will try to rewrite it as <tt>expr.opConv()</tt>. The compiler will then chose
the opConv that returns the desired type.
For implicit conversions, the compiler will look for a conversion constructor of the target type that take a
matching argument, and isn't flagged as explicit. If it doesn't find one, it will try to call the
opImplConv on the source type that returns the target type.
<pre>
class MyObj
{
double myValue;
// Allow MyObj to be implicitly created from double
MyObj(double v) { myValue = v; }
// Allow MyObj to be implicitly converted to double
double opImplConv() const { return myValue; }
// Allow MyObj to be created from int, but only explicitly
MyObj(int v) explicit { myValue = v; }
// Allow MyObj to be converted to int, but only explicitly
int opConv() const { return int(myValue); }
}
</pre>
This should only be used for value conversions and not reference casts. That is, the methods are expected to return
a new instance of the value with the new type.
If a reference cast is desired, i.e. a different type of handle to the same object instance, then the opCast
method should be implemented instead. The compiler will attempt to rewrite an expression <tt>cast<type>(expr)</tt>
as <tt>expr.opCast()</tt>, and chose the opCast overload that returns a handle of the desired type. Here too the
opImplCast can be implemented instead if the reference cast is allowed to be performed implicitly by the compiler.
<pre>
class MyObjA
{
MyObjB \@objB;
MyObjC \@objC;
MyObjB \@opCast() { return objB; }
MyObjC \@opImplCast() { return objC; }
const MyObjB \@opCast() const { return objB; }
const MyObjC \@opImplCast() const { return objC; }
}
</pre>
An example where the opCast/opImplCast operator overloads come in handy is when extending a type without directly
\ref doc_script_class_inheritance "inheriting" from it.
\see \ref conversion, \ref doc_adv_inheritappclass
*/
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