Convert double to string C++?

Question

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How do I convert a double into a string in C++?

I want to combine a string and a double and g++ is throwing this error:

main.cpp: In function ‘int main()’:
main.cpp:40: error: invalid operands of types ‘const char [2]’ and ‘double’ to binary ‘operator+’

Here is the line of code which it is throwing the error on:

storedCorrect[count] = "("+c1+","+c2+")";

storedCorrect[] is a string array, and c1 and c2 are both doubles. Is there a way to convert c1 and c2 to strings to allow my program to compile correctly?

Answer 1

You can't do it directly. There are a number of ways to do it:

1. Use a std::stringstream:

   std::ostringstream s;
   s << "(" << c1 << ", " << c2 << ")";
   storedCorrect[count] = s.str()
   

2. Use boost::lexical_cast:

   storedCorrect[count] = "(" + boost::lexical_cast<std::string>(c1) + ", " + boost::lexical_cast<std::string>(c2) + ")";
   

3. Use std::snprintf:

   char buffer[256];  // make sure this is big enough!!!
   snprintf(buffer, sizeof(buffer), "(%g, %g)", c1, c2);
   storedCorrect[count] = buffer;
   

There are a number of other ways, using various double-to-string conversion functions, but these are the main ways you'll see it done.