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Inline Class Member Functions

A function defined in the body of a class declaration is an inline function.

In the following class declaration, the Account constructor is an inline function. The member functions GetBalance, Deposit, and Withdraw are not specified as inline but can be implemented as inline functions.

// Inline_Member_Functions.cpp
class Account
    Account(double initial_balance) { balance = initial_balance; }
    double GetBalance();
    double Deposit( double Amount );
    double Withdraw( double Amount );
    double balance;

inline double Account::GetBalance()
    return balance;

inline double Account::Deposit( double Amount )
    return ( balance += Amount );

inline double Account::Withdraw( double Amount )
    return ( balance -= Amount );
int main()

In the class declaration, the functions were declared without the inline keyword. The inline keyword can be specified in the class declaration; the result is the same.

A given inline member function must be declared the same way in every compilation unit. This constraint causes inline functions to behave as if they were instantiated functions. Additionally, there must be exactly one definition of an inline function.

A class member function defaults to external linkage unless a definition for that function contains the inline specifier. The preceding example shows that these functions need not be explicitly declared with the inline specifier; using inline in the function definition causes it to be an inline function. However, it is illegal to redeclare a function as inline after a call to that function.