Re: [boost] [review] string convert

Subject: Re: [boost] [review] string convert
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2011-05-04 11:32:46

Gordon Woodhull wrote:
> int i = convert_cast<int>(s); // default behavior: might throw
> optional<int> i = convert_cast<int>(s, use_optional_instead_of_throwing_);
> int i = convert_cast<int>(s, 17); // won't throw; can't tell if conversion successful

Why do you prefer the tags rather than just adding the error policy to the name?

And why do you prefer template specialisation rather than just adding the type to the name?

(Keep It Simple.)

int i = must_parse_int(s);  // Personally I use "must" to mean "else throw", but I 
                            // wouldn't want to impose that on anyone else.
optional<int> i = try_parse_int(s);  // I've never used optional<> here, but I tend to 
                                     // write try_* for things that return a boolean to 
                                     // indicate success.
int i = parse_int_with_default(s, 17);

But per my last posts, anyone can easily write those in whatever style they want, if they 
have the core function, e.g.

template <typename ITER>
void parse_int(ITER begin, ITER end, int& i, bool& success)
{
  ....
}

int must_parse_int(std::string s)
{
  int i; bool success;
  parse_int(s.begin(),s.end(),i,success);
  if (!success) throw ParseError();
  return i;
}

optional<int> try_parse_int(std::string s)
{
  int i; bool success;
  parse_int(s.begin(),s.end(),i,success);
  return success ? i : optional<int>();
}

int parse_int_with_default(std::string s, int def)
{
  int i; bool success;
  parse_int(s.begin(),s.end(),i,success);
  return success ? i : def;
}

(I'm confused by the following, which look pointless; have I missed something?)
> int i = convert_cast<int>(s, 17, throw_even_though_i_specified_a_failback_);
> optional<int> i = convert_cast<int>(s, 17, use_optional_instead_of_throwing_);
> pair<bool,int> i = convert_cast<int>(s, 17, fallback_and_report_success_);

Regards,  Phil.