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.
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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
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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).
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