The code below shows 2 solutions (std::to_string and std::stringstream) that convert an int m_currentSoundTime to std::string. Is std::to_string or std::stringstream faster?
// Compute current sound time in minute and convert to string
stringstream currentTime;
currentTime << m_currentSoundTime / 60;
m_currentSoundTimeInMinute = currentTime.str();
or
m_currentSoundTimeInMinute = to_string( m_currentSoundTime / 60 );
In any reasonable library implementation to_string will be at least as fast as stringstream for this. However, if you wanted to put 10 ints into a string, stringstream will likely be faster. If you were to do to_string(a) + ", " + to_string(b) + /*...*/ every operation would probably cause an allocation and a copy from the previous string to the new allocation - not true with stringstream.
More importantly, it's pretty obvious from your example code that to_string is cleaner for dealing with converting a single int to a string.
to_string(a) returns a temporary, which can be modified by + ", ", which itself returns a temporary... So in fact, it is likely that your chained calls with to_string will be faster (no virtual dispatch, ...).
to_string(a) likely has a capacity just large enough for what it's currently holding. So when you + ", ", even if you don't need an extra string temporary, the allocation the current string owns needs to be remade to be larger, the old data copied to the new allocation, etc. Repeat for each +. The implementation could (should) use realloc... but it will have the same problem, inconsistently.std::string should use amortized allocation. It may, of course, lead to one or two reallocations... but there is no telling whether that will be more than std::stringstream, and don't forget that std::stringstream::str() will allocate a string (if you need to).
This blog post tests several int-to-string conversion methods (using GCC 4.7 on Ubuntu 13.04). In this
case to_string is somewhat slower than stringstream. But this probably depends strongly on the compiler and std library.
to_string, and it just delegates to snprintf. Simpler, I guess, but indeed surprising.
In this case to_string is somewhat slower than stringstream. In the blog post to_string is faster than stringstream. Did I get something wrong here?