How do I concatenate multiple C++ strings on one line?

C# has a syntax feature where you can concatenate many data types together on 1 line.

string s = new String();
s += "Hello world, " + myInt + niceToSeeYouString;
s += someChar1 + interestingDecimal + someChar2;

What would be the equivalent in C++? As far as I can see, you'd have to do it all on separate lines as it doesn't support multiple strings/variables with the + operator. This is OK, but doesn't look as neat.

string s;
s += "Hello world, " + "nice to see you, " + "or not.";

The above code produces an error.

From stackoverflow

• s += "Hello world, " + "nice to see you, " + "or not.";
  

  Those character array literals are not C++ std::strings - you ned to convert them:

  s += string("Hello world, ") + string("nice to see you, ") + string("or not.");
  

  To convert ints (or any other streamable type) you can use a boost lexical_cast or provide your own function:

  template <typename T>
  string Str( const T & t ) {
     ostringstream os;
     os << t;
     return os.str();
  }
  

  You can now say things like:

  string s = "The meaning is " + Str( 42 );
  

  Ferruccio : You only need to explicitly convert the first one: s += string("Hello world,") + "nice to see you, " + "or not.";

  anon : Yes, but I couldn't face explaining why!

  bb : boost::lexical_cast - nice and similar on your Str function:)

• boost::format

  or std::stringstream

  std::strinstream msg;
  msg << "Hello world, " << myInt  << niceToSeeYouString;
  msg.str(); // returns std::string object
  

  Marcin : +1 for boost::format

• #include <sstream>
  #include <string>
  
  std::stringstream ss;
  ss << "Hello, world, " << myInt << niceToSeeYouString;
  std::string s = ss.str();
  

  Take a look at this Guru Of The Week article from Herb Sutter: The String Formatters of Manor Farm

• You would have to define operator+() for every data type you would want to concenate to the string, yet since operator<< is defined for most types, you should use std::stringstream.

  Damn, beat by 50 seconds...

  Tyler McHenry : You can't actually define new operators on built-in types like char and int.

• Your code can be written as,

  s = "Hello world," "nice to see you," "or not."
  

  ...but I doubt that's what you're looking for. In your case, you are probably looking for streams:

  std::stringstream ss;
  ss << "Hello world, " << 42 << "nice to see you.";
  std::string s = ss.str();
  

  j_random_hacker : Your 1st example is worth mentioning, but please also mention that it works only for "concatenating" literal strings (the compiler performs the concatenation itself).