hi all:

I want erase a stringstream' content for input new data to it.

example:
std::stringstre am stm;
stm<<"this is a string";

std::cout<<stm. str();
// here print:this is a string

// do something here of the stm, i don't know .....
stm<<"not a string";

std::cout<<strm .str();
// I want print "not a string",...