jett jett - 1 year ago 107
C++ Question

Concatenating strings (and numbers) in variadic template function

I am attempting to write a function that takes a variety of strings or numbers (that work with

and concatenate them. I've got it working with just strings, but I am having trouble with specializing depending on input as string or number.

My code is called like this:

stringer("hello", "world", 2, 15, 0.2014, "goodbye", "world")

And here is what I've got:

inline std::string stringer(const std::string &string)
return string;

template <typename T, typename... Args>
inline std::string stringer(const std::string &string, T &&val, Args &&...args)
return stringer(string+std::to_string(val), std::forward<Args>(args)...);

template <typename... Args>
inline std::string stringer(const std::string &string, Args &&...args)
return stringer(string, std::forward<Args>(args)...);

Currently it is breaking on any more than one string added unless the following are all numbers (due to the to_string). How can I specialize based on string or number to make the above work? Thanks.

Answer Source
inline std::string const& to_string(std::string const& s) { return s; }

template<typename... Args>
std::string stringer(Args const&... args)
    std::string result;
    using ::to_string;
    using std::to_string;
    int unpack[]{0, (result += to_string(args), 0)...};
    return result;
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