What Do const&, &, and &&& Specifiers Mean for Member Functions in C ?

Const&, &, and &&: Specifiers for Member Functions in C

Recently, a thorough examination of the boost::optional API revealed intriguing lines featuring member function specifiers const&, &, and &&. While experimentation demonstrated the apparent functionality of such declarations, their intricacies remained unclear.

Explaining the Specifiers

• const&: Restricts usage to const, non-const, and lvalue objects. Example:

<code class="cpp">const A a = A();
*a;</code>

• &: Limits usage to non-const objects. Example:

<code class="cpp">A a;
*a;</code>

• &&: Exclusively applicable to rvalue objects. Example:

<code class="cpp">*A();</code>

Rationale Behind the Distinction

These specifiers enable precise control over member function overloads. They allow developers to tailor function accessibility based on the object's constancy and value category (lvalue/rvalue). This granularity ensures code efficiency by optimizing function selection for specific scenarios.

For in-depth insights into "rvalue reference for *this," refer to the comprehensive post at the provided link.

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