Add std::to_string

Author: mortennobel

README.md

@@ -352,6 +352,7 @@ s1 == "hello world" // Comparison, also <, >, !=, etc.
 s1[0]; // 'h' 
 s1.substr(m, n); // Substring of size n starting at s1[m] 
 s1.c_str(); // Convert to const char* 
+s1 = to_string(12.05); // Converts number to string
 getline(cin, s); // Read line ending in '\n' 
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