http://en.wikipedia.org/wiki/Hygienic_macro http://en.wikipedia.org/wiki/Hygienic_macro Hygenic macros are limited to 'safe' operations. They let you extend th

http://en.wikipedia.org/wiki/Hygienic_macro http://en.wikipedia.org/wiki/Hygienic_macro Hygenic macros are limited to 'safe' operations. They let you extend the language without creating opportunities for incredibly complex and hard to debug stuff like you can do with un-hygenic macros, for example C macros.