Do you use sprintf in your code ? Did you see it even in “written in C++” called code ? Well, ok it is way to format your numbers to a string and perhaps it is liked most for its convenience and ease of use. There are some reasons not to use yout get by experience or by researching the web.
Recently I start using boost::format as an alternative to sprintf.
Suppose you have to program some hardware device for example a motion controller by sending a dedicated ASCII character string over some wire interface to trigger certain action like
std::string command = "PAX=10000;SPX=30000;AMX=100000;BGX"; int ret = device.sendCommand(command);
Where usally the character X for selecting differnt motion stages and any of the numbers can change during runtime. So how to do this ?
char* commmand; const char* axis = "X"; sprintf(command,"PA%s=%d;SP%s=%d;AM%s=%d;BG%s", axis, pos, axis, speed, axis, acc, axis); int ret device.sendCommand(std::string(command));
std::stringstream stream; std::string axis ="X"; stream << "PA" << axis << "=" << pos << ";" <<"SP" <<axis <<"=" <<speed <<";" <<"AM" <<axis"=" <<acc <<"BG" <<axis; int ret = device.sendCommand(stream.str());
Using a stringstream object is definitely type safe C++, but gets unhandy and error prone very quick. Especially in this case. You get the point why many people go for sprintf.
With boost::format it turns out that we can implement the example like this:
boost::format cmdMove("PA%1%=%2%;SP%1%=%3%;AM%1%=%4%;BG%1%"); std::string command = (cmdMove % axis % pos % speed % accel).str(); int ret device.sendCommand(command);
First we create a boost::format object, which we can reuse or implement as a member in our command classs etc. The ctor takes a string and the variable arguments are marked by so called positional arguments which allows for reuse or reordering. When assiging the command string the arguments are fed with the % operator into the object. The argument axis ( %1%) is used four times in this case, which led to less typing and cleaner code.
With boost::format you can also realize posix-printf styles, but in a type safe way.
You can find more info at http://www.boost.org/doc/libs/1_58_0/libs/format/