Re: [Cpptool-develop] Abt Sven's question on scope

[Baptiste L. <gai...@fr...>]

Thanks. Do you know if in the following declarations:
1) the temporary is visible after the if statement  (I don't think so,
but...)
2) if the scope of the temporary declared in the condition is the same as
the scope of the temporary declared in the then/else/iteration statement


if ( int x = 3, y = x )
{
    int x;        // is it legal ? (different scope ?)
}
// is x visible here ?


while ( int x = 3, y = x  )
{
    int x;        // is it legal ? (different scope ?)
}
// is x visible here ?


A tricky one to deal with will be the 'for' statement, since all compilers
do not follow the standard (and gcc is even trickier since it allows both
non-conformant usage (with a warning) and conformant usage...

There is also the matter of the using declaration, which promise to be 'fun'
to deal with...

Baptiste.

--- Original Message -----
From: "Rohith Rajagopal" <man...@ho...>
To: <cpp...@li...>
Sent: Wednesday, November 20, 2002 6:23 AM
Subject: [Cpptool-develop] Abt Sven's question on scope


> This is what the ANSI C++ std has to say:
> http://www.comnets.rwth-aachen.de/doc/c++std/basic.html
> The example below will probably answer the question.
>
> 1 Every  name  is  introduced  in  some portion of program text called a
> declarative region, which is the largest part of the program in  which
that
> name  is  valid,  that  is, in which that name may be used as an
> unqualified name to refer to the same entity.  In general,  each
particular
>   name is valid only within some possibly discontiguous portion of program
> text called its scope.  To determine the scope of a  declaration,  it is
> sometimes convenient to refer to the potential scope of a declaration.
The
> scope of a declaration is the same as  its  potential  scope unless the
> potential scope contains another declaration of the same name.  In that
> case, the potential scope of  the  declaration in the inner (contained)
> declarative region is excluded from the scope of the declaration in the
> outer (containing) declarative region.
>
> 2 [Example: in
>           int j = 24;
>           int main()
>           {
>                   int i = j, j;
>                   j = 42;
>           }
>   the identifier j is declared twice as a name (and  used  twice).   The
> declarative  region  of  the first j includes the entire example.  The
> potential scope of the first j begins immediately  after  that  j  and
> extends to the end of the program, but its (actual)  scope excludes the
text
> between the , and the }.  The declarative region  of  the  second
> declaration of j (the j immediately before the semicolon) includes all the
> text between { and }, but its potential scope excludes the  declaration
of
> i.  The scope of the second declaration of j is the same as its potential
> scope.  ]