c++ syntax of create an instance

Question

class class_name instance;

class_name instance;

The above all work with cl.exe, but is it standard,is it the same with all other compilers?

outis · Accepted Answer · 2010-10-14 12:22:56Z

3

class class_name instance; is allowed by the elaborated-type-specifier nonterminal in the C++ grammar. It's hard to point to a particular section of the standard that tells you this, since even in the appendix that gives the C++ grammar it's rather spread out, but the production basically goes (with many steps elided):

declaration-statement
    -> type-specifier declarator ;
    -> elaborated-type-specifier declarator ;
    -> class identifier declarator ;
    -> class identifier unqualified-id ;
    -> class class_name instance ;

class_name instance ;, in comparison, is produced using the simple-type-specifier non-terminal.

declaration-statement
    -> type-specifier declarator ;
    -> simple-type-specifier declarator ;
    -> type-name unqualified-id ;
    -> class_name instance ;

edited Oct 14, 2010 at 12:22

answered Oct 14, 2010 at 12:17

outis

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Yakov Galka · Accepted Answer · 2010-10-14 11:50:44Z

2

Yes, It's standard and means the same thing. class T and T mean the same thing in C++. The syntax comes from C where struct T and T don't mean the same thing.

answered Oct 14, 2010 at 11:50

Yakov Galka

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