C ++ 11 implements a simple lexical_cast, and 11 implements lexical_cast.

C ++ 11 implements a simple lexical_cast, and 11 implements lexical_cast.

There is a lexical_cast in boost that can be used for conversion between basic types in a unified manner, such as conversion between strings to numbers, numbers to strings, bool, and strings and numbers. Boost: lexical_cast is easy to use:

# Include <boost/lexical_cast.hpp> # include <iostream> # include <string> # define ERROR_LEXICAL_CAST 1 int main () {using boost: lexical_cast; int a = 0; double B = 0.0; std: string s = ""; int e = 0; try {// ----- string --> value a = lexical_cast <int> ("123 "); B = lexical_cast <double> ("123.12"); // ----- value --> string s = lexical_cast <std: string> ("123456.7 "); // ----- Exception Handling demo e = lexical_cast <int> ("abc");} catch (boost: bad_lexical_cast & e) {// bad lexical cast: source type value cocould not be interpreted as target std: cout <e. what () <std: endl; return ERROR_LEXICAL_CAST;} std: cout <a <std: endl; // output: 123 std :: cout <B <std: endl; // output: 123.12 std: cout <s <std: endl; // output: 123456.7 return 0 ;}View Code

The lexical_cast method is missing in c ++ 11, but c ++ 11 provides some basic type conversion methods, such as to_string, atoi, atof, etc, however, we cannot use a common method to convert the basic types. Therefore, I want to convert the basic types by using lexical_cast similar to boost, this is also a development plan for our c ++ community.

Since c ++ 11 has provided some convenient methods, what I want to do is to combine them and provide a unified lexical_cast method.

The implementation idea is also very simple. There are mainly the following types of conversions: 1. number to String Conversion; 2. string to number conversion; 3. convert bool and string; 4. convert a number to bool. The specific implementation code is as follows:

#include <type_traits>#include <string>#include <cstdlib>#include <algorithm>#include <stdexcept>#include <cctype>#include <cstring>using namespace std;namespace detail{    const char* strue = "true";    const char* sfalse = "false";    template <typename To, typename From>    struct Converter    {    };    //to numeric    template <typename From>    struct Converter<int, From>    {        static int convert(const From& from)        {            return std::atoi(from);        }    };    template <typename From>    struct Converter<long, From>    {        static long convert(const From& from)        {            return std::atol(from);        }    };    template <typename From>    struct Converter<long long, From>    {        static long long convert(const From& from)        {            return std::atoll(from);        }    };    template <typename From>    struct Converter<double, From>    {        static double convert(const From& from)        {            return std::atof(from);        }    };    template <typename From>    struct Converter<float, From>    {        static float convert(const From& from)        {            return (float)std::atof(from);        }    };    //to bool    template <typename From>    struct Converter<bool, From>    {        static typename std::enable_if<std::is_integral<From>::value, bool>::type convert(From from)        {            return !!from;        }    };    bool checkbool(const char* from, const size_t len, const char* s)    {        for (size_t i = 0; i < len; i++)        {            if (from[i] != s[i])            {                return false;            }        }        return true;    }    static bool convert(const char* from)    {        const unsigned int len = strlen(from);        if (len != 4 && len != 5)            throw std::invalid_argument("argument is invalid");        bool r = true;        if (len == 4)        {            r = checkbool(from, len, strue);            if (r)                return true;        }        else        {            r = checkbool(from, len, sfalse);            if (r)                return false;        }        throw std::invalid_argument("argument is invalid");    }    template <>    struct Converter<bool, string>    {        static bool convert(const string& from)        {            return detail::convert(from.c_str());        }    };    template <>    struct Converter<bool, const char*>    {        static bool convert(const char* from)        {            return detail::convert(from);        }    };    template <>    struct Converter<bool, char*>    {        static bool convert(char* from)        {            return detail::convert(from);        }    };    template <unsigned N>    struct Converter<bool, const char[N]>    {        static bool convert(const char(&from)[N])        {            return detail::convert(from);        }    };    template <unsigned N>    struct Converter<bool, char[N]>    {        static bool convert(const char(&from)[N])        {            return detail::convert(from);        }    };    //to string    template <typename From>    struct Converter<string, From>    {        static string convert(const From& from)        {            return std::to_string(from);        }    };}template <typename To, typename From>typename std::enable_if<!std::is_same<To, From>::value, To>::type lexical_cast(const From& from){    return detail::Converter<To, From>::convert(from);}template <typename To, typename From>typename std::enable_if<std::is_same<To, From>::value, To>::type lexical_cast(const From& from){    return from;}

It took more than an hour before and after, and a basic type conversion class was completed. Test the code again:

void test(){    cout<<lexical_cast<int>(1)<<endl;    cout << lexical_cast<int>("1") << endl;    cout << lexical_cast<long>("1") << endl;    cout << lexical_cast<string>(1) << endl;    cout << lexical_cast<bool>(1) << endl;    cout << lexical_cast<double>("1.2") << endl;    cout << lexical_cast<float>("1.2") << endl;    string s = "true";    cout << lexical_cast<bool>(s) << endl;    char* p = "false";    cout << lexical_cast<bool>(p) << endl;    const char* q = "false";    cout << lexical_cast<bool>(q) << endl;    cout << lexical_cast<bool>("false") << endl;    cout << lexical_cast<bool>("test") << endl;}int main(){    try    {        test();    }    catch (const std::exception& e)    {        cout << e.what() << endl;    }    return 0;}

Test results: