Editing Reference (C++) (section)

=== Lvalue reference ===
The declaration of the form:

 <Type>& <Name>

where <code><Type></code> is a [[Data type|type]] and <code><Name></code> is an [[identifier]] is said to define an identifier whose type is '''[[Value (computer science)#lrvalue|lvalue]] reference to <code><Type></code>'''.<ref>[[#cpp-std|ISO/IEC 14822]], clause 9.3.3.2, paragraph 1.</ref>

Examples:
<syntaxhighlight lang="cpp">
int a = 5;
int& r_a = a;

extern int& r_b;
</syntaxhighlight>

Here, <code>r_a</code> and <code>r_b</code> are of type "lvalue reference to <code>int</code>"

<syntaxhighlight lang="cpp">int& Foo();</syntaxhighlight>

<code>Foo</code> is a function that returns an "lvalue reference to <code>int</code>"

<syntaxhighlight lang="cpp">void Bar(int& r_p);</syntaxhighlight>

<code>Bar</code> is a function with a reference parameter, which is an "lvalue reference to <code>int</code>"

<syntaxhighlight lang="cpp">class MyClass { int& m_b; /* ... */ };</syntaxhighlight>

<code>MyClass</code> is a <code>class</code> with a member which is lvalue reference to <code>int</code>

<syntaxhighlight lang="cpp">
int FuncX() { return 42 ; };
int (&f_func)() = FuncX;
int (&&f_func2)() = FuncX; // essentially equivalent to the above
</syntaxhighlight>

<code>FuncX</code> is a function that returns a (non-reference type) <code>int</code> and <code>f_func</code> is an ''[[aliasing (computing)|alias]]'' for <code>FuncX</code>

<syntaxhighlight lang="cpp">const int& ref = 65;</syntaxhighlight>

<code>[[const (computer programming)|const]] int& ref</code> is an lvalue reference to <code>const int</code> pointing to a piece of storage having value 65.

<syntaxhighlight lang="cpp">
int arr[3];
int (&arr_lvr)[3] = arr;
int (&&arr_rvr)[3] = std::move(arr);
typedef int arr_t[3];
int (&&arr_prvl)[3] = arr_t{}; // arr_t{} is an array prvalue
int *const & ptr_clv = arr; // same as int *const & ptr_clv = &arr[0];
int *&& ptr_rv = arr;
// int *&arr_lv = arr; // Error: Initializing an lvalue reference to non-const type with an rvalue
</syntaxhighlight>

<code>arr_lvr</code> is a reference to an array. When initializing a reference to array, array-to-pointer conversion does not take place, but it does take place when initializing a reference to pointer. Since array-to-pointer conversion returns a prvalue, only lvalue references to <code>const</code> and rvalue references can be initialized with its result. Similarly, when initializing a reference to function, function-to-pointer conversion does not take place (see <code>f_func</code> above), but it does take place when initializing a reference to function pointer:

<syntaxhighlight lang="cpp">
int FuncX() { return 42 ; };
int (*const &pf_func)() = FuncX; // same as int (*const &pf_func)() = &FuncX;
int (* &&pf_func2)() = FuncX;
</syntaxhighlight>