Can i overload operator for character arrays

In fact it is, in a very real sense, the only guideline; the rest are just special cases. If you define arithmetic operators, maintain the usual arithmetic identities. You should provide arithmetic operators only when they make logical sense to users. However adding two dates makes no sense: what does it mean to add July 4, to June 5, ? Similarly it makes no sense to multiply or divide dates, so you should not define any of those operators.

You should provide mixed-mode arithmetic operators only when they make logical sense to users. Similarly date - duration could also return a Date. But duration - date does not make sense at the conceptual level what does it mean to subtract July 4, from 35 days?

If you provide constructive operators, they should return their result by value. If it returns by reference, you will probably run into lots of problems figuring out who owns the referent and when the referent will get destructed. See the next bullet for more on this point. If you provide constructive operators, they should not change their operands.

If you provide constructive operators, they should allow promotion of the left-hand operand at least in the case where the class has a single-parameter ctor that is not marked with the explicit keyword. For example, if your class Fraction supports promotion from int to Fraction via the non- explicit ctor Fraction::Fraction int , and if you allow x - y for two Fraction objects, you should also allow 42 - y.

In practice that simply means that your operator- should not be a member function of Fraction. Typically you will make it a friend , if for no other reason than to force it into the public: part of the class , but even if it is not a friend, it should not be a member. In general, your operator should change its operand s if and only if the operands get changed when you apply the same operator to intrinsic types.

Similar comments for x-- and --x. For example, these expressions should have the same observable behavior, including the same result. For example, these two expressions should have the same result and neither should change p.

Subscript operators generally come in pairs; see on const -overloading. For example, after an assignment, the two objects should be equal. Avoid overloading the comma operator: x, y. The overloaded comma operator does not have the same ordering properties that it has when it is not overloaded, and that confuses users.

This is called the Doctrine of Least Surprise. Use common sense. Just remember the ultimate goals of operator overloading: to make life easier for your users, in particular to make their code cheaper to write and more obvious.

How do I create a subscript operator for a Matrix class? Use operator rather than operator[]. The operator approach is sometimes better because whenever the optimal layout for a given application happens to be something other than dense, row-major, the implementation is often significantly easier using the operator approach compared to the [][] approach. Create nested class Matrix::Row. Change Matrix::operator[] unsigned row so it returns an object of class Matrix::Row , e. Class Matrix::Row then defines its own operator[] unsigned col which turns around and calls, you guessed it, Matrix::operator unsigned row, unsigned col.

Should I design my classes from the outside interfaces first or from the inside data first? Because the new operator returns a pointer to the objects it allocates, the program must define a pointer with suitable scope to access and delete those objects.

Once the pointer AnotherArray goes out of scope in the example, the object can no longer be deleted. The new-expression the expression containing the new operator does three things:. Locates and reserves storage for the object or objects to be allocated.

When this stage is complete, the correct amount of storage is allocated, but it's not yet an object. Initializes the object s. Once initialization is complete, enough information is present for the allocated storage to be an object. Returns a pointer to the object s of a pointer type derived from new-type-id or type-id.

The program uses this pointer to access the newly allocated object. The new operator invokes the function operator new. For arrays of any type, and for objects that aren't class , struct , or union types, a global function, ::operator new , is called to allocate storage. Class-type objects can define their own operator new static member function on a per-class basis. When the compiler encounters the new operator to allocate an object of type T , it issues a call to T::operator new sizeof T or, if no user-defined operator new is defined, ::operator new sizeof T.

It's how the new operator can allocate the correct amount of memory for the object. An option in the grammar allows specification of new-placement see the Grammar for new Operator.

The new-placement parameter can be used only for user-defined implementations of operator new ; it allows extra information to be passed to operator new. The original intention of the new-placement field was to allow hardware-dependent objects to be allocated at user-specified addresses. Although the preceding example shows only one argument in the new-placement field, there's no restriction on how many extra arguments can be passed to operator new this way. Even when operator new has been defined for a class type T , you can use the global operator new explicitly, as in this example:.

Notice that the code in the body of the member function is the same. Only the return data type of the function has changed. This change will allow the assignment statement to work and a reference works on the right side of an assignment statement as well. Both of the code examples above will now compile and run correctly. But this change also introduces a different problem. What if the string object is constant? The first code example should definitely work with a constant string.

All we're doing is printing the characters of the string, we're not trying to modify the string at all:. There is a lot going on here. If they are not the same, we start by deleting the current character array, so that we can copy the new character array in from rhs. We copy lnth and capacity directly, then we make a new c array, and copy the characters one at a time from rhs. Finally, we want to return the current object.

We can't say return this , since that would return a pointer rather than the object itself. Once we have done this, you might expect that if we want to write a function like. Home » More About Classes » Overloading assignment. Collapse menu 1 Basics 1.