value semantics

MoveConstructible

Suppose that

• T is a object or reference type to be supplied by a c++ program instantiating a template
• u denotes an identifier
• rv denotes an rvalue of type T

We say that a type T is MoveConstructible when the following is true:

Expression	Post-conditions
T u = rv;	The value of u is equivalent to the value of rv before the initialization.
T(rv)	The value of T(rv) is equivalent to the value of rv before the initialization.

Note that there is no condition on the value of rv after these operations

CopyAssignable

Suppose that:

• T is a object or reference type to be supplied by a c++ program instantiating a template
• u denotes an identifier
• v denotes an lvalue of type (possibly const) T or an rvalue of type const T.

We say that a type T is CopyAssignable when the following is true:

Expression	Return type	Return value	Post-conditions
t = v	T&	t	The value of t is equivalent to the value of v. The value of v is unchanged.

CopyConstructible

Suppose that:

• T is a object or reference type to be supplied by a c++ program instantiating a template
• u denotes an identifier
• v denotes an lvalue of type (possibly const) T or an rvalue of type const T.

We say that a type T is CopyConstructible when the following is true:

• The type T is MoveConstructible.

Expression	Post-conditions
T u = v;	The value of u is equivalent to the value of v. The value of v is unchanged.
T(v)	The value of T(v) is equivalent to the value of v. The value of v is unchanged.

Additionally, the xpression v.~T() must be valid, and for lvalue v, the expression &v must have type T* or const T* and evaluate to the address of v.

We say that a type T is MoveAssignable when the following is true:

Expression	Return type	Return value	Post-conditions
t = rv	T&	t	If t and rv do not refer to the same object, the value of t is equivalent to the value of rv before the assignment. The new value of rv is unspecified.