Detailed Description
A type is Assignable if it is possible to copy objects of that type and to assign values to variables.
- Refinement Of:
- Associated Types:
- Notation:
X | A type that is a model of Assignable |
x, y | Object of type X |
- Definitions:
- Valid Expressions:
| Name | Expression | Type requirements | Return type |
| Copy constructor | X(x) | | X |
| Copy constructor | X x(y);
X x = y;
| | |
| Assignment | x = y [1] | | X& |
| Swap | adobe::swap(x,y) | | void |
- Expression Semantics:
| Name | Expression | Precondition | Semantics | Postcondition |
| Copy constructor | X(x) | | | X(x) is a copy of x [2] |
| Copy constructor | X(x) | | | X(x) is a copy of x [2] |
| Copy constructor | X x(y);
X x = y;
| | | x is a copy of y [2] |
| Assignment | x = y [1] | | | x is a copy of y [2] |
| Swap | adobe::swap(x,y)[3] | | Equivalent to {
X tmp = x;
x = y;
y = tmp;
}
| |
- Complexity Guarantees:
- Invariants:
- Type(s) Modeling this Concept:
-
- Notes:
- [1] One implication of this requirement is that a
const type is not Assignable. For example, const int is not Assignable: if x is declared to be of type const int, then x = 7 is illegal. Similarly, the type pair<const int, int> is not Assignable.
- [2] The reason this says "
x is a copy of y", rather than "x == y", is that operator== is not necessarily defined: equality is not a requirement of Assignable. If the type X is EqualityComparable as well as Assignable, then a copy of x should compare equal to x.
- [3]
adobe::swap will not throw an exception for an assignable type. For types with remote parts, adobe::swap must be specialized to swap the remote parts.
- [4] It is assumed that adobe::swap() will not throw an exception. Items with remote parts much specialize swap as described in swap.
- See Also:
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