src/HOL/Data_Structures/RBT.thy
2015-11-15 nipkow 2015-11-15 tuned white space
2015-11-02 nipkow 2015-11-02 tuned names and optimized comparison order
2015-10-18 nipkow 2015-10-18 added 2-3 trees (simpler and more complete than the version in ex/Tree23)
2015-09-23 nipkow 2015-09-23 tuned
2015-09-22 nipkow 2015-09-22 added red black trees