🚀 go-pugleaf

In article <1992Sep2.171859.852@lucid.com>, jss@lucid.com (Jerry Schwarz) writes:
|> In article <1992Sep2.143007.5655@bnrmtl.bnr.ca>, john@bnrmtl.bnr.ca (John Hickin) writes:
|> |> 
|> |> A compiler using the const temporary approach and a thoughtful programmer
|> |> can combine to make code like that of the String example safer:
|> |> 
|> |>    class String { public:
|> |>        operator const char*(); // NON-const
|> |>        String( const char* );
|> |>        ...
|> |>    };
|> |> 
|> 
|> Making the function that gives the pointer to char a non-const is a mistake.
|> The function may modify the underlying representation, but it certainly
|> does not modify the represented character sequence.  There is no
|> reason that I shouldn't be able to apply it to a const String
|> 
|> |>    String h( "hello " ), w( "world" );
|> |>    const char* p = h + w;
|> 
|> A careful programmer might have written
|> 
|> 	const String h("hello "), w(" world") ;
|> 
|> and be surprised that  (const char*)h isn't allowed.

Well, until the language support for abstract const is solidified, I
suggest the following:

    class String { public:
       operator char*();             // NON-const
       operator const char*() const; // const
       String( const char* );
       ...
    };

A non-const string can be converted to a non-const char*, a const string
can only be converted to a const char*.  If only conversion to a const
char* is desired, then I agree with Jerry that the non-const version should
be eliminated.

|> I believe the use of the implicitly invoked conversion operator
|> obscures the issue of lifetime of temporaries and that we should 
|> be writing the above example out in full as.
|> 
|> 	const char* p = (h+w).pchar();

I tend to agree, although I am open to opposing views.

|> 
|>   -- Jerry Schwarz

-- 

- Pablo

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Pablo Halpern             (617) 290-3542
HP Waltham                pabloh@hpwarq.wal.hp.com

I am self-employed, so my opinions *do* reflect those of my employer.
However, they may not reflect the opinions of my client.
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