Is this code valid C++?

Is the followi开发者_如何学Gong code valid C++?

const int  var = 10;
{ 
   int  var[var]; // why doesn't this give any error ?
}

Note : The code compiles on my g++ compiler.

As-is? No. If it were in the body of a function? Yes.

The first line declares an integer constant named var with a value of 10.

The braces begins a new block. Within that block, a new variable is declared, named var, which is an array of int with a size equal to the value of the integer constant previously declared as var (10).

The key is that var refers to the first variable until after the second variable named var is fully declared. Between the semicolon following the second declaration and the closing brace, var refers to the second variable. (If there was an initializer for the second variable, var would begin to refer to the second variable immediately before the initializer.)

Yes the code is valid C++. Non-local var is visible up to the point of declaration of local var.

So int var[var] defines a local array of 10 integers.

Yes the code is valid C++ It is a concept of SCOPE : Hiding Names

 const int  var = 10;
  { 
   int  var[var]; // why doesn't this give any error ?
  }

I think this link clears your doubt

IN C++:

http://msdn.microsoft.com/en-US/library/9a9h7328%28v=VS.80%29.aspx

In C :

http://publib.boulder.ibm.com/infocenter/comphelp/v8v101/index.jsp?topic=%2Fcom.ibm.xlcpp8a.doc%2Flanguage%2Fref%2Fzexscope_c.htm

If u want deep knowledge On this : Go for this link,here the information is about Lexical versus dynamic scoping

http://en.wikipedia.org/wiki/Scope_%28programming%29

but in your code : "Scope ::" of visibility of var .Here It differs like local and non-local variable. Inside braces { x=1; } local variable . where as here {y=1;{x=1;}} ,here it differs.

helpful links

http://msdn.microsoft.com/en-us/library/b7kfh662%28VS.80%29.aspx

http://www.awitness.org/delphi_pascal_tutorial/c++_delphi/c++_scope_variables.html