References

• when we use the term reference, we mean “lvalue reference.”
• A reference type “refers to” another type
• A reference is not an object. Instead, a reference is just another name for an already existing object. It’s very important.
  • So all operations on that reference are actually operations on the object.
  • We can’t define neither a reference to a reference nor pointer to reference. (虽然有时候看起来好像可以，但那实际上用的还是这个object本身)
• reference and the object must match exactly. With two exceptions.
  • one is “const reference”. actually no such “const reference”.

int i = 1;
int &ri = i;

We bind the reference to its initializer. Because there is no way to rebind a reference, so references must be initialized.

Reference to const

“ri is bound to a temporary object”. (C++ Primer, p62)

• refer to a const type. nonconst reference can’t refer to an const type, cause the language ban the way that change the underlying object through reference.
• refer to a literal
• const reference can refer to nonconst type, but can’t a nonconst reference to refer a const type.
• can refer to an expression. not allowed with nonconst reference.

Attention

1. const reference 只说了 reference 是 const，可没说 the underlying 是什么

2. with the “temporary” feature, I compile some cases and find:

• when a const reference refer to a const or nonconst variable, they hold same address.
• but when refer to an expression or literal, it have a new address.

terms	means
const reference	abbreviate the phrase “reference to const”