Here are the essential rules for operator overloading in C++:
General Rules:
- Only overload existing operators: You can't create new operators, but you can redefine the behavior of existing ones for user-defined types (classes, structures, unions).
- At least one operand must be user-defined: Both operands can't be built-in types.
- Maintain operator precedence and associativity: Don't alter the default order of operation evaluation or how operators group operands.
- Use member functions or friend functions:
- Member functions: Suitable for most cases, giving access to object data.
- Friend functions: Used for global operators or when member functions are not suitable.
Operator-Specific Rules:
- Unary vs. Binary operators:
- Unary operators in member functions have no arguments.
- Binary operators in member functions have one argument.
- Operators in friend functions have two arguments.
- Overloadable and Non-Overloadable operators:
- Overloadable: Arithmetic, comparison, assignment, increment/decrement, bitwise, logical, indexing, function call, stream insertion/extraction.
- Non-Overloadable:
::
,.
(member selection),.*
(member selection through pointer to function),?:
(ternary operator).
- Friend function limitations: Cannot overload certain operators like
=
,()
,[]
,->
.
Additional Guidelines:
- Intuitive behavior: Make sure overloaded operators act as users expect, aligning with their natural meaning.
- Avoid ambiguity: Don't overload operators in a way that leads to confusion or unintended behavior.
- Consider the scope and purpose: Only overload operators when it genuinely enhances your code's readability, maintainability, or expressiveness.
By following these rules and guidelines, you can effectively leverage operator overloading to create expressive and maintainable C++ code.
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