How to form a C++ string from concatenations of string literals?

I would like concatenate string literals and ints, like this:

string message("That value should be between " + MIN_VALUE + " and " + MAX_VALUE);

But that gives me this error:

error: invalid operands of types ‘const char*’ and ‘const char [6]’ to binary ‘operator+’|

What 开发者_如何学Pythonis the correct way to do that? I could split that in 2 string declarations (each concatenating a string literal and a int), but that's ugly. I've also tried << operator.

Thanks

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You should probably use stringstream for this.

#include <sstream>

std::stringstream s;
s << "This value shoud be between " << MIN_VALUE << " and " << MAX_VALUE;
message = s.str();

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The c++ way to do this is to use a stringstream then you can use the << operator. It will give you a more consistent code feel

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There are many ways to do this, but my favourite is:

string message(string("That value should be between ") + MIN_VALUE + " and " + MAX_VALUE);

That extra string() around the first literal makes all the difference in the world because there is an overloaded string::operator+(const char*) which returns a string, and operator+ has left-to-right associativity, so the whole thing is turned into a chain of operator+ calls.

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#include <sstream>
#include <string>

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



std::string message = "That value should be between " + Str( MIN_VALUE ) 
                       + " and " + Str( MAX_VALUE );

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You probably want to use a stringstream like this:

std::stringstream msgstream;
msgstream << "That value should be between " << MIN_VALUE << " and " <<  MAX_VALUE;
std::string message(msgstream.c_str());