C++ Operators

C++ supports a lot of operators! These include operators that you likely think of, such as arithmetic and logical operators, as well as conversion operators.

Both C++ and Ruby support operator overriding, although C++ supports more of them. The sections below describe how to map C++ operators to Ruby operators.

Arithmetic Operators

Most overridden C++ arithmetic operators can be overridden in Ruby.

C++	Ruby
+	+
-	-
*	*
/	/
%	%
++	Not overridable
–	Not overridable

Assignment Operators

Ruby does not support overriding assignment operators.

C++	Ruby
=	assign
+=	Not overridable
-=	Not overridable
*=	Not overridable
/=	Not overridable
%=	Not overridable

Bitwise Operators

C++ and Ruby support overriding the same bitwise operators.

C++	Ruby
&	&
|	|
~	~
<<	<<
>>	>>

Comparison (Relational) Operators

C++ and Ruby support overriding the same comparison operators.

C++	Ruby
==	==
!=	!=
>	<
<	>
>=	>=
<=	<=

Logical Operators

Ruby allows the ! operator to be overridden but not && or ||.

C++	Ruby
&&	Not overridable
||	Not overridable
!	!

Other Operators

C++ and Ruby support overriding an additional set of operators.

C++	Ruby
[]	[]
	[]= (if reference)
()	call
,	Not overridable
<<	<<
>>	>>

If a C++ class defines an [] operator that returns a reference, then in it should be mapped to two Ruby operators: [] and []=.

C++ classes that support the () operator are known as functors. Ruby supports overriding the .() operator by defining a call function. Note this isn’t quite the same as C++ because it is invoked via .() and not () – notice the . before the ().

Conversion Operators

C++ allows users to define explicit and implicit conversion operators or functions. These are used to convert a class to a different types. For example:

class Money
{
public:
    Money(float amount);
    operator float() const;
};

The operator double() const; is a user defined conversion function that converts a Money instance to a double. Following Ruby conventions, these conversion functions should be exposed as to_ method, in this case to_f.