Lazy evaluation with ostream C++ operators
- by SavinG
I am looking for a portable way to implement lazy evaluation in C++ for logging class.
Let's say that I have a simple logging function like
void syslog(int priority, const char *format, ...);
then in syslog() function we can do:
if (priority < current_priority)
return;
so we never actually call the formatting function (sprintf).
On the other hand, if we use logging stream like
log << LOG_NOTICE << "test " << 123;
all the formating is always executed, which may take a lot of time.
Is there any possibility to actually use all the goodies of ostream (like custom << operator for classes, type safety, elegant syntax...) in a way that the formating is executed AFTER the logging level is checked ?
