• Dave <Dave_member pathlink.com> Mar 22 2007
• Walter Bright <newshound digitalmars.com> Mar 22 2007

Dave <Dave_member pathlink.com> writes:

Walter Bright Wrote:

 Andrei Alexandrescu (See Website For Email) wrote:
 Walter Bright wrote:
 Turning off sync is cheating - D's readln does syncing.


 I don't know exactly what sync'ing does in C++, but probably it isn't 
 the locking that you are thinking of.


 I think it means bringing the iostream I/O buffer in to sync with the 
 stdio I/O buffer, i.e. you can mix printf and iostream output and it 
 will appear in the same order the calls happen in the code.
 


That's exactly what it does... Quite a few times I've had to 'optimize' C++
iostream code using sync_with_stdio().

 D's readln is inherently synced in this manner.


Which of course begs the question -- Could an overload be added so it doesn't
sync (not the default)? Might be worth a test, and if the difference is
significant keep it.

Walter Bright <newshound digitalmars.com> writes:

Dave wrote:
 Walter Bright Wrote:
 Andrei Alexandrescu (See Website For Email) wrote:
 Walter Bright wrote:
 Turning off sync is cheating - D's readln does syncing.


 the locking that you are thinking of.


 stdio I/O buffer, i.e. you can mix printf and iostream output and it 
 will appear in the same order the calls happen in the code.


 That's exactly what it does... Quite a few times I've had to 'optimize' C++
iostream code using sync_with_stdio().
 
 D's readln is inherently synced in this manner.


 Which of course begs the question -- Could an overload be added so it doesn't
sync (not the default)? Might be worth a test, and if the difference is
significant keep it.


Since the data has to be buffered anyway, might as well use stdio's 
buffer. I don't know why iostream felt the need to reimplement the 
buffers - certainly it isn't for performance <g>.