Re: Thoughts about a standard string_argument to unify char* and std::string

Alberto Ganesh Barbati <>
Fri, 30 Mar 2007 11:27:09 CST
Gennaro Prota ha scritto:

On Wed, 28 Mar 2007 16:09:26 GMT, Daniel Svensson wrote:

Many functions like ifstream::open() should be operloaded in C++09 to
handle std::string as well plain char pointers.

Do you find that to be a good idea?

Personally I think so. In fact this trick is so simple and convenient
that I would like it proposed for boostification.

To not force mutliple
definitions (and implementations) of the same function,

What do you mean by "multiple definitions"? (As to the
implementation(s), it's all the usual dance of forwarding to a common
"back-end" function --not a real problem IMHO)

This trick has a narrower scope than forwarding and because of that it's
much simpler to use and apply. Writing one function that works for both
char* and strings is just a one-token change and it allows you to forget
putting c_str() all over the place. I find this very useful. Don't you
hate to write:

  ostringstream path;
  // compose path
  ifstream file(path.str().c_str()); // ugly

or worse:

  string name;
  ifstream file((name + ".txt").c_str()); // ugly

Well, if the c_str() could be left out, I would be much happier.

[Note: please let's not focus on ifstreams and pathnames specifically...
I know there are better alternatives like boost::filesystem, but cases
like the one above pop up in a lot of places.]

It's also easily extensible:

template <class T>
const char* get_c_str(const T& str)
   return str.c_str();

class string_arg
    const char* _str;

    string_arg(const char* str)
        : _str(str)

    template <class T>
    string_arg(const T& str)
        : _str(get_c_str(str))

    operator const char*() const { return _str; }
    const char* c_str() const { return _str; }

By specializing the get_c_str() template, user-provided string-like
classes can also be supported. The library need not even be aware of
that, one single signature per function needs to be provided and will
work in any case.

Just my opinion,


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