ios_base::setf
ios_base::setf
void setf(fmtflags mask);
fmtflags setf(fmtflags fmtfl, fmtflags mask);
The first member function effectively calls flags
(mask | flags())
(set selected bits), then returns the previous format flags. The second member function effectively calls flags(mask & fmtfl, flags() & ~mask)
(replace selected bits under a mask), then returns the previous format flags.