Semicolon After Class Declaration Braces

Semicolon after class declaration braces

The semi-colon after the closing brace in a type declaration is required by the language. It's been that way since the earliest versions of C.

And yes, people do indeed do the declaration you just put up there. It's useful for creating scoped types inside of methods.

void Example() {
  struct { int x; } s1;
  s1.x = 42;

  struct ADifferentType { int x; };
}

In this case, I think it's clear why the semi-colons are needed. As to why it's needed in the more general case of declaring in the header file I'm unsure. My guess is that it's historical and was done to make writing the compiler easier.

Semicolon after class declaration

Explain, please, why is it possible to use semicolon here and what does ';' means in these context

Semicolons are optional in ruby. This means that using them is actually valid syntax. Having a newline is enough for the parser to separate statements. In the case you mention the semicolon is required as there is not a newline as a statement separator.

The following are all valid options:

class Dog
end

class Dog;
end

class Dog; end

The following is invalid (with ruby >= 2.3 this seems to be fine though)

class Dog end

For class or method definitions with an empty body using one line with a semicolon separator is idiomatic in ruby. If you have a body you'll usually omit the semicolon and place the content on a new line.

UPD: I thought, that

Java's syntax parser doesn't allow as much flexibility as ruby's parser. A class or method definition in Java is strict syntax which requires a newline after the class name and before the definition body.

When is a semicolon after } mandated in c/c++?

int a[2] = {1,2}, j = 5;

When initialization of array or structure are done with {} all the subsequent variables are declared after ,.

Edit: As you changed your question; ; is mandatory after the class, enum, initialization syntax declarations.

class A {};  // same for `struct
enum E {};   // enum class (c++0x)
int a[] = {1,2};  // array or object initialization

And as per comment by @rubenvb:

do {} while(condition);

C++ Semicolon after class, struct, enum,... useless but compilers still emit errors?

It's a leftover from C. You can declare variables after cladd/struct/enum declaration. the code:

class A{};
A a;

Is identical to:

class A{} a;

The compiler needs the ; to know you don't want to declare variables after the class declaration.

When should I use a semicolon after curly braces?

You use a semicolon after a statement. This is a statement:

var foo = function() {  alert("bar");};

Class declaration confusion - name between closing brace and semi-colon

rect is the name of a variable (an object in this case).

It is exactly as if it had said:

  int rect;

except instead of int there is a definition of a new type, called a CRectangle. Usually, class types are declared separately and then used as

  CRectangle rect;

as you are probably familiar with, but it's perfectly legal to declare a new type as part of a declaration like that.

And yes, it works for structs:

  struct SRectangle { int x, y; } rect;

In fact you don't even have to give the type a name if you don't plan to use it again:

  struct { int x, y; } rect;

that's called an "anonymous struct" (and it also works for classes).

When do we need to put semicolon after curly brackets? i.e.: };

"Anonymous classes enable you to make your code more concise. They enable you to declare and instantiate a class at the same time. They are like local classes except that they do not have a name. Use them if you need to use a local class only once."

Java - Anonymous Classes

Instead of doing something like this:

class MyThread extends Thread {
    @Override
    public void run(){
        // something
    }
}
...
Thread myThread= new MyThread();

You can sorten your code by doing it this other way using anonymous classes.

Thread myThread=new Thread(){
   @Override
   public void run(){
      // something
   }
};

Auto insert semicolon after class definition in Codelite

CodeLite does not do that by default and there is no setting that you can modify to do that.

You can however, achieve this in two other ways:

Use the class wizard:

Create your class using the 'Class Wizard': Right click on a folder in the tree view and select New class

Use the abbreviations plugin

From the menu bar: plugins->abbreviations->settings
Click on the new entry button (green plus icon)
Name it "class" (or a name of your choice) and paste the following code:
class | {
public:
};
Click "Save"
Now when typing in the editor class hit: Ctrl-ENTER and you will see this entry - select it and it will added to the text editor for you.

NOTE: the | marker indicates where CodeLite will place the caret, You can have multiple carets. So the above example can be expanded to something like this:

class | {
public:
    |(){}
    ~|(){}
};

Now, when CodeLite adds this snippet to the editor, you will get 3 carets. Typing the class name will add them in all three locations

NOTE 2: The above was tested using CodeLite 11.0.8 (git latest), but it should work with CodeLite 11.0 as well

HTH,

Eran, Author of CodeLite IDE