From: Yukihiro Matsumoto <matz@...>
Date: 2010-04-01T00:22:49+09:00
Subject: [ruby-dev:40883] Re: [Feature #2673] the length for an enumerator generated by Array#permutation and Array#combination

Hi,

In message "Re: [ruby-dev:40882] [Feature #2673] the length for an enumerator generated by Array#permutation and Array#combination"
    on Thu, 1 Apr 2010 00:11:02 +0900, Marc-Andre Lafortune <redmine@ruby-lang.org> writes:

|I wanted to propose that Enumerator had a #length/#size method that would return nil or the size of the enumeration, when known. My (unfinished) proposal was to allow a block though, so that the result would always be valid, even if the source object was modified. Object#to_enum would accept a block and use that to calculate the length.

This propose has been suspended for 1.9.2 since the resule may not be
trustworthy considering the source modification after generating
enumerator.  I am not sure passing block is a good idea or not, yet.
It's not intuitive for me at the first glance.

							matz.