Standard Template Library Programmer's Guide

mem_fun_t, mem_fun_ref_t, mem_fun1_t

Utilities

Concepts

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.

Notation

X A type that is a model of Assignable

x, y Object of type X

Valid expressions

Name	Expression	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	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; }

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.