🚀 go-pugleaf

Dawn Koffman <dkoffman@cnj.digex.net> writes:

>Question 1 

>The ARM says:

>    "The type of this in a member function of class X is X *const unless 
>     the member function is declared const or volatile; in those cases, 
>     the type of this is const X *const and volatile X *const, respectively."

>9.4.2 of the 4/95 draft standard says:

>    "The type of this in a member function of class X is X*.  If the member
>     function is declared const, the type of this is const X*, if the member
>     function is declared volatile, the type of this is volatile X*, and
>     if the member function is declared const volatile, the type of this 
>     is const volatile X*."

>Why has the type of this changed from X* const to X*, and from const X* const 
>to const X*?


The draft also says "this" is a non-lvalue expression. Since "this"
isn't an lvalue, const-ness is irrelevant. You can't assign to it or
take its address, so const would have no effect for any operation you
could perform. That is, const has a meaning only for lvalues.


>Question 2

>9.4.2 of the draft standard goes on to say:

>    "In a const member function, the object for which the function is called 
>     is accessed through a const access path; therefore, a const member 
>     function shall not modify the object and its non-static data members."

>This section of the draft standard doesn't say anything to indicate that 
>mutable data members may be modified inside const member functions.

The section on "mutable" (7.1.1) says it nullifies a const specifier
on the containing object and that you may assign to the data member.
It would be nice if the section on "this" mentioned "mutable".
--
Steve Clamage, stephen.clamage@eng.sun.com

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