[DOC]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42751 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

bignum.c

@@ -6545,6 +6545,8 @@ rb_big_size(VALUE big)
  *  (The bit position of the bit 2**n is n+1.)
  *  If there is no such bit (zero or minus one), zero is returned.
  *
+ *  I.e. This method returns ceil(log2(int < 0 ? -int : int+1)).
+ *
  *     (-2**10000-1).bit_length  #=> 10001
  *     (-2**10000).bit_length    #=> 10000
  *     (-2**10000+1).bit_length  #=> 10000
@@ -6615,6 +6617,8 @@ rb_big_bit_length(VALUE big)
  *  (The bit position of the bit 2**n is n+1.)
  *  If there is no such bit (zero or minus one), zero is returned.
  *
+ *  I.e. This method returns ceil(log2(int < 0 ? -int : int+1)).
+ *
  *     (-2**12-1).bit_length     #=> 13
  *     (-2**12).bit_length       #=> 12
  *     (-2**12+1).bit_length     #=> 12