If you define your member function inside class declaration , they are implicitly inline.
The inline function is supposed to improve the performance by embedding the function body to calling place and so reduce calling cost. It has two disadvantages: add the size of the program and change of the inline function will make caller recompile.
Suppose we have a method DoSomething() will read user input and the input should be a number. If user did not input a number, the method fail to finish its job, so the other code rely on the job should not execute and program should do something about it like show a message to the user, in software programming .
The login information can store in session or cookie. When store in session, the default expire time is when browser is closed.
Change the default by set the session.cookie_lifetime option in php.ini.
In MySQL, you can specify a column as auto_increment, the value will increment 1 at each insert. SQL Server also provide similar thing. Oracle using SEQUENCE and NEXTVAL to do the job.
Create a SEQUENCE:
Oracle provide PL/SQL packages let you extend the database functionality . You can write you own package or utilize the packages shipped with Oracle release.Oracle supplies all kinds of packages, familiar with these packages is a must-have skill of DBA.
Packages is a collection of different program objects include procedures, functions, variables, constants, cursors, exceptions etc.
enum(enumeration) is a user-defined type consisting of a set of enumerators( enumerator --- named integer constant)
Simple enum definition:
When use generate lexer with flex and compile it as cplusplus file, you will get an error like this:
But when compile as c file it will be no problem, if you see the generated c file , you will see:
I always have the question: How the interface find its implementation ? In the calling code we always declare object with the interface name, Never need to declare the implementation class. We never explicitly tell the compiler which implementation to use.
The answer is , compiler don't know which implementation to use. When you declare a interface , there is no instance created, you have to new something and assign that instance to the interface. And the instance can be anything that implement the interface.The answer is , compiler don't know which implementation to use. When you declare a interface , there is no .
In java extends declaration syntax we often see something like this:
The question mark also show up on other place, inside an angle bracket. It means any class, its a wildcard. Its the Generic of Java. It called bounded wildcard.