I agree: cout << endl should flush the buffer. It does when stdout is a tty. For some reason, the buffering becomes much more aggressive when the stdout is a pipe.
On Fri, Aug 22, 2014 at 6:14 AM, Juergen Sauermann < juergen.sauerm...@t-online.de> wrote: > Hi David, > > thanks, included in SVN 443. > > This is interesting because I normally use something like *out << endl *which > should have flushed the buffer. > On the other hand *⍞* is somewhat special because it prints a prompt but > no *endl* so that the user enters her input > on the same line. > > I have added a few *cout << flush* for* ⎕/⍞ *so maybe the patch isn't > needed anymore (I guess unbuffered output > is slightly slower than buffered output). > > /// Jürgen > > > On 08/22/2014 05:11 AM, David Lamkins wrote: > > Oops. Here's the same patch, but inquiring about the correct file > descriptor. > > (It'll work either way in some cases...) > > > On Thu, Aug 21, 2014 at 8:06 PM, David Lamkins <da...@lamkins.net> wrote: > >> I've been puzzled by the interaction between GNU APL and aplwrap, in >> which ⎕ and ⍞ output doesn't appear until APL prompts for input. This >> behavior is bad for the case where the program tries to emit periodic >> progress messages during long computations. >> >> It turns out that the C++ std lib is responsible for this behavior. While >> cerr is unbuffered, cout holds onto buffered content for as long as >> possible. (Apparently it only does this when stdout is not a terminal, as >> running the same test in a shell window does not exhibit the aggressive >> buffering behavior.) >> >> I learned that cout's buffering behavior can be be changed using the >> call: >> >> std::cout.setf(std::ios::unitbuf); >> >> This can be called sometime before running the main APL loop, and will >> cause cout's buffer to be flushed at each <<, the same as cerr. >> >> The attached patch (GNU APL SVN 441) runs the 'unitbuf' code only in >> the case that stdin is not a tty. >> >> >> >> -- >> "The secret to creativity is knowing how to hide your sources." >> Albert Einstein >> >> >> http://soundcloud.com/davidlamkins >> http://reverbnation.com/lamkins >> http://reverbnation.com/lcw >> http://lamkins-guitar.com/ >> http://lamkins.net/ >> http://successful-lisp.com/ >> > > > > -- > "The secret to creativity is knowing how to hide your sources." > Albert Einstein > > > http://soundcloud.com/davidlamkins > http://reverbnation.com/lamkins > http://reverbnation.com/lcw > http://lamkins-guitar.com/ > http://lamkins.net/ > http://successful-lisp.com/ > > > -- "The secret to creativity is knowing how to hide your sources." Albert Einstein http://soundcloud.com/davidlamkins http://reverbnation.com/lamkins http://reverbnation.com/lcw http://lamkins-guitar.com/ http://lamkins.net/ http://successful-lisp.com/
