Question

I have this class:

template<typename T> class Parser
{
    public:
        Parser() : count(0) {}
        virtual void parse(const string&);
        void get_token(void);
    private:
        T result;
        char token;
        string expression;
        int count;
};

now had the class not been generic, had the result been say, a double, I would have used this method to detect numbers.

while((strchr("1234567890.",token))
{
     /* add token to a "temp" string */
     /* etc. etc. */
}

result = atof(temp.c_str());

But since result is generic, I can’t use any method like atof and atoi etc.

What do I do?

Answer 1

Boost has this functionality built-in:

 #include <boost/lexical_cast.hpp>

 void Parser<T>::get_token() {
     std::string token = ...;
     result = boost::lexical_cast<T>(token);
 }

Add exception handling as required.

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Or, perhaps you don’t want to use Boost for some reason:

void Parser<T>::get_token() {
     std::string token = ...;

     std::stringstream ss;
     ss << token;
     ss >> result;
}

Check the error state of ss as required.

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More expansive answers may be found on this related question, though it discusses only int specifically.