WORLD follows the Google C++ Style Guide
Japanese:
http://www.textdrop.net/google-styleguide-ja/cppguide.xml
English:
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml

However, there are several exceptions about variable names.
Since these names are generally used in the acoustic signal processing,
I employed these names as the variable names.
(1) x represents the input signal.
(2) y represents the signal after processing.
(3) fs represents sampling frequency.
(4) f0 represents fundamental frequency (including f0 contour).
(5) t0 represents fundamental period.
(6) vuv represents voiced/unvoiced information.
(7) tmp_* represents temporal value. In WORLD, 
    "temporal" is used as another meaning.

I prioritized compatibility with C language over the style guide.
