What is the purpose of anonymous { } blocks in C style languages?

Question

What is the purpose of anonymous { } blocks in C style languages (C, C++, C#)

Example -

void function()
{

  {
    int i = 0;
    i = i + 1;
  }

          


        

Answer 1

It limits the scope of variables to the block inside the { }.

Answer 2

Scoping of course. (Has that horse been beaten to death yet?)

But if you look at the language definition, you see patterns like:

• if ( expression )   statement
• if ( expression )   statement   else   statement
• switch ( expression )   statement
• while ( expression )   statement
• do   statement   while ( expression ) ;

It simplifies the language syntax that compound-statement is just one of several possible statement's.

---

compound-statement:   { statement-list_opt }

statement-list:

• statement
• statement-list   statement

statement:

• labeled-statement
• expression-statement
• compound-statement
• selection-statement
• iteration-statement
• jump-statement
• declaration-statement
• try-block

Answer 3

I use it for blocks of code that need temporary variables.

Answer 4

By creating a new scope they can be used to define local variables in a switch statement.

e.g.

switch (i)
{
    case 0 :
        int j = 0;   // error!
        break;

vs.

switch (i)
{
    case 0 :
    {
        int j = 0;   // ok!
    }
    break;

Answer 5

As far as I understand, they are simply for scoping. They allow you to reuse variable names in the parent/sibling scopes, which can be useful from time to time.

EDIT: This question has in fact been answered on another Stack Overflow question. Hope that helps.

Answer 6

As the previous posters mentioned, it limits the use of a variable to the scope in which it is declared.

In garbage collected languages such as C# and Java, it also allows the garbage collector to reclaim memory used by any variables used within the scope (although setting the variables to null would have the same effect).

{
    int[] myArray = new int[1000];
    ... // Do some work
}
// The garbage collector can now reclaim the memory used by myArray