vicente.botet wrote:
Hi, ----- Original Message ----- From: "Phil Richards" <news@derived-software.ltd.uk> To: <boost@lists.boost.org> Sent: Saturday, March 06, 2010 11:59 AM Subject: Re: [boost] [program_options]
On Fri, 2010-03-05 at 09:21 +0300, Vladimir Prus wrote:
Matthew Herrmann wrote:
I'd vote to replace const char* everywhere in the program options interface with std::string. (excluding the "char* argv[]" of course) 'replace'? I'm afraid, over my dead body only. I surely don't want implicit conversion to happen, and bloat the code, for every name and description of the option.
Well, I certainly don't want to see anybody's dead body, but here is the code for setting name:
option_description::set_name(const char* _name) { std::string name(_name); string::size_type n = name.find(','); if (n != string::npos) { assert(n == name.size()-2); m_long_name = name.substr(0, n); m_short_name = '-' + name.substr(n+1,1); } else { m_long_name = name; } return *this; }
I can't see how taking a std::string const& as an argument has any detrimental effect on conversions or code bloat. The std::string version of set_name would just remove the first line of the function (creating the temporary "name"), and use _name throughout the function body.
Sorry, you have said 'replace' -- which means changing const char* to std::string (const, &, whatever). That would meant creating a string at each call site where you pass const char*, which is more code than required to just push pointer to the stack.
Description is even simpler: it just uses the const char* argument as a parameter to a std::string constructor. Accepting a std::string const& instead of a const char* will have minimal overheads (possibly one extra temporary string creation).
But maybe I'm missing something obvious?
The fact that currently the implementation use a temporary string doesn't means that we can not change the implementation. The interface with a string const reference involves already an allocation and deallocation when you have a const char*.
What about having both overloads? const char * is the best for literals, while string cont& is the best for strings variables.
void option_description::set_name(string const&_name); void option_description::set_name(const char* _name);
As I've said already, I don't remember why this is not provided, and will have to think about it. - Volodya