Another 'Why & Why Not' Question

[udit99]

Code mentioned in a book fr showing how 2 do Assignment Op. O/Loading.


#include<iostream.h>
class alpha
{
int data;
public:

alpha(){}
alpha(int d)
{
data=d;
}
void display()
{
cout<<data;
}
alpha operator =(alpha& a)
{
data=a.data;
cout<<"Assignment op. invoked";
return alpha(data);
}
};

void main()
{
alpha a1(37);
alpha a2;
a2=a1; //invokes O/Loaded Ass. Op.
cout<<"\n a2";a2.display();

alpha a3=a2; // Does not invoke O/Loaded Ass. Op.
cout<<"\na3=";a3.display();

}

What I wanna know here is tt in the Operator O/Loading bit


alpha operator =(alpha& a)
{
data=a.data;
cout<<"Assignment op. invoked";
return alpha(data);
}

the guy has specified alpha as a return type...I mean why shud it be alpha...y cant it b just a void return type.....after all...we're only going 2 b doing

alpha a3=a2

so y isnt the following sufficient

void operator =(alpha& a)
{
data=a.data;
cout<<"Assignment op. invoked";
}

[udit99]

Y do all this when we're only going 2 b doing
a3=a2

[kedaman]

In fact it should be alpha& not alpha. As all the operators actually returns something you can construct expressions that does more than one assignment, for instance:

int a,b,c;
a=b=c=0;

instead of

a=0;
b=0;
c=0;

reason why you would need it to be a reference instead of a copy, is for those cases where you pass assigned values:

Dosomething(a=10);

It's nothing you absolutely have to do, it's just that it's more convenient if the operators act like they should

[parksie]

#include<iostream.h>

How old is your book?

[udit99]

Not Quite Old by Indian Standards......I'm in India now....homeland...frgot 2 change the Location in Profile..its actually TurboC++ by robert Lafore....

Y ?....nowadays do they only write #include<iostream>...tts y ?

[parksie]

Uh...tts?

The new iostream library fits in better with the rest of the standard library because it's all template-based. In practice it shouldn't make much difference to the actual code you write, but it makes it easier to implement for the library writers.