Issue #3089 has been updated by Yuki Sonoda.

Assigned to set to Yukihiro Matsumoto

> I learned the hard way I better ask if there is a valid reason for this artificial limit for #combination ?

hmm, matz, is this behavior intended?  If not, I regard the limitation as a bug. It means, The patch can be merged into ruby 1.9.2.
----------------------------------------
http://redmine.ruby-lang.org/issues/show/3089

----------------------------------------
http://redmine.ruby-lang.org