Is `bar` an Lvalue or an Rvalue in `void foo(string&& bar)`?

Understanding Rvalue References and Lvalues

Consider the following code:

void foo(string&& bar){
    string* temp = &bar;

    cout << *temp << " @:" << temp << endl;
}

Here, the question arises: Is the variable bar an rvalue or an lvalue?

Answer: Bar is an Lvalue

Despite having the type "rvalue reference to string," bar is still an lvalue because it has a name. An lvalue, by definition, is any expression that evaluates to a named storage location.

Differentiating Rvalue References from Lvalue References

While you can perform similar operations on rvalue and lvalue references within expressions, they differ significantly in what can bind to them:

• Lvalue references: Can bind to both lvalues and rvalues.
• Rvalue references (named): Can only bind to rvalues.

Significance of Rvalue References

The distinction between rvalue and lvalue references becomes crucial when dealing with function parameters of rvalue reference type. Rvalue references convey valuable information: the value they refer to is an rvalue, which means it's temporary and will be destroyed upon expression completion. This allows for safe treatment of the referenced value as an rvalue.

Conclusion

The distinction between rvalue and lvalue references lies not in their usability within expressions but in what can be bound to them. Rvalue references provide crucial information about the nature of the referenced value, allowing efficient resource management and appropriate treatment as an rvalue.

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