>class String
>{
> public:
>   String  (const char* s);
>};
>
>void foo (explicit const String& str)
>{
>  // do whatever
>}
>int main ()
>{
>   char* s = "hello";
>   foo (s); // I would like this to produce a compile time error
>}

I don't think the above example is legal.  It is, however, not
necessary.  When you invoke the function foo, the compiler must create
a temporary String object from the char pointer parameter.

If String::String(const char*) were declared explicit, I think this
would prohibt the compiler from creating the temporary and thus the
function call will produce a compile error.

Someone please correct me if I am wrong.

DV
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I think being able to use the keyword explicit in
the declaration of a constructor is a great idea.
Now my question is can it be also used in parameter
specification.

Example:

class String
{
 public:
    .
    .
   String  (const char* s);
    .
    .

};


void foo (explicit const String& str)
{
  // do whatever
}


int main ()
{
   .
   .
   char* s = "hello";
   foo (s); // I would like this to produce a compile time error
   .
   .
}


 Is this feature available in the latest C++ language specification ?
Does it break something ? Is it hard to implement in the compiler ?

If there are no problems with this feature. I think it would offer
greater flexibility in controlling implicit conversions.

--
Mohammad Jafar
jafar@esp.bellcore.com
(732) 699-8352
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Mohammad Jafar wrote:

> I think being able to use the keyword explicit in
> the declaration of a constructor is a great idea.

Me too

> Now my question is can it be also used in parameter
> specification.
>
> Example:

[const char* convertible to String]

> void foo (explicit const String& str)
> {
>   // do whatever
> }
>
> int main ()
> {
>    .
>    .
>    char* s = "hello";
>    foo (s); // I would like this to produce a compile time error
>    .
>    .
> }
>
>  Is this feature available in the latest C++ language specification ?
> Does it break something ? Is it hard to implement in the compiler ?

No, no, no(trivial)

> If there are no problems with this feature. I think it would offer
> greater flexibility in controlling implicit conversions.

I don't think it's usefull enough to include it.

Either viewing a const char* as a String is ok or not. If not,
then you shouldn't define a non-explicit ctor.

--

Valentin Bonnard                mailto:bonnardv@pratique.fr
info about C++/a propos du C++: http://www.pratique.fr/~bonnardv/
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