[Cs3] #pragma once

[Mikhail Nesterenko]

CS3 students,

somebody asked about 

 #pragma once

It is a non-standard (but widely supported by compilers) preprocessor
directive and is an alternative to include guards for protection
against multiple inclusion. It is even considered to speed up
compilation. However, as non-standard its use it discouraged if
writing for portability. For example, google style guide prohibits its
use:

   http://google-styleguide.googlecode.com/svn/trunk/cppguide.html?showone=Windows_Code#Windows_Code

However, our textbook seems to use it. clang and g++ seem to compile
it without problems.

Thanks,
-- 
Mikhail