CODEWITHSUNDEEP
c++
Dew
Dew

Reputation: 3143

Function Overloading

In C++, Why function overloading not implemented on the basis of return type?

Upvotes: 1

Views: 408

Answers (5)

rainshark
rainshark

Reputation: 45

When calling a function, its return type is not involved. So it would be meaningless to implement function overloads with different return types.

Upvotes: 0

James Kanze
James Kanze

Reputation: 153919

Because C++ has implicit conversions which make it more or less impossible most of the time, e.g.:

int f();
char f();

double d = f();

It's possible to simulate overloading on the return type some of the time, by using a proxy object:

int doFInt();
char doFChar();

struct Proxy
{
    template<typename T> operator T() const
    {
        return static_cast<T>(doFInt());
    }
};
template<>
Proxy::operator char() const { return doFChar(); }

Proxy f();

double d = f();  //  Calls doFInt().

About the only time something like this is worth the bother, however, is when it can be made truely generic; something like a getAttribute function where the attribute is always stored as a string, and the generic form of the function uses boost::lexical_cast to convert to the target type.

Upvotes: 1

P&#233;ter T&#246;r&#246;k
P&#233;ter T&#246;r&#246;k

Reputation: 116266

Because it is legal to ignore return values, thus the compiler would not always be able to realistically decide which overload to invoke.

Consider

void foo();
int foo();
long foo();

...
foo(); // which function to call here???

But even if the return value is assigned, it may not be possible to choose between equivalent overloads when a conversion is required:

double d = foo(); // and here???

Upvotes: 15

Shamim Hafiz - MSFT
Shamim Hafiz - MSFT

Reputation: 22094

Consider the case:

double Fun()
{
}


int Fun()
{
}

Since it's not compulsory to assign a return value from a function, a call to Fun() would be ambiguous since the compiler wont know which Fun() to call.

Upvotes: 1

sergico
sergico

Reputation: 2621

Because the compiler would not always been able to decide which function to select.

Upvotes: 0

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