Reputation: 3167
Unfortunately, in my current project I can't use boost, so I am trying to imitate the behavior of boost::lexical_cast
(minus most of the error checking boost does). I have the following functions, which work.
// Convert a string to a primitive, works
// (Shamelessly taken from another stack overflow post)
template <typename T>
T string_utility::lexical_cast(const string &in)
{
stringstream out(in);
T result;
if ((out >> result).fail() || !(out >> std::ws).eof())
{
throw std::bad_cast();
}
return result;
}
// Convert a primitive to a string
// Works, not quite the syntax I want
template <typename T>
string string_utility::lexical_cast(const T in)
{
stringstream out;
out << in;
string result;
if ((out >> result).fail())
{
throw std::bad_cast();
}
return result;
}
I was hoping to be able to use the same syntax for both for consistency, but I can't figure it out.
Converting a string to a primitive is fine.
int i = lexical_cast<int>("123");
The otherway, however, looks like this:
string foo = lexical_cast(123);
// What I want
// string foo = lexical_cast<string>(123);
Edit: Thanks ecatmur I had to switch the template parameters around, but the following does exactly what I want.
template<typename Out, typename In> Out lexical_cast(In input)
{
stringstream ss;
ss << input;
Out r;
if ((ss >> r).fail() || !(ss >> std::ws).eof())
{
throw std::bad_cast();
}
return r;
}
Upvotes: 1
Views: 206
Reputation: 157534
The basic template code for lexical_cast
is:
template<typename In, typename Out> Out lexical_cast(In in) {
stringstream ss;
ss << in;
if (ss.fail()) throw bad_cast();
ss >> out;
return out;
}
Add error checking and specialisations for (In == string), etc. as desired.
Upvotes: 4