Assignable Assignable Category: utilities Component type: concept 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 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 swap(x,y)   Equivalent to { X tmp = x; x = y; y = tmp; }   Complexity guarantees Invariants Models int 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. See also DefaultConstructible Copyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation