Re: [boost] Re: filesystem library const usage

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-08-01 17:04:09

At 12:03 PM 8/1/2002, Jurko wrote:

 >How about this example:
 >
 >// Some kind of a container class. Has a non const
 >// member function void add( const Value& ) which adds
 >// another value to the the container.
 >class A;
 >
 >// A useful utility function.
 >void foo( const A& );
 >
 >// A function that returns an object of class A by value.
 >const A bar( void );
 >
 >Now we couldn't do this:
 >foo( bar().add( someMissingValue ) );
 >
 >And in order to achieve the same effect we would have to
 >eather copy the object returned by bar (potentially very
 >expensive!) or give up using the useful foo function in this
 >case (assuming we can't or don't want to change how foo()
 >or bar() work).
 >
 >But then again I'm using the const value return rule and never
 >came up against a real-world case where it presented even a
 >slight problem.

As Bill Kempf pointed out, there are classes where that sort of non-const 
operation chaining is an intended and desirable use.  But that doesn't seem 
to be the case with several of the path functions which return by value.

--Beman