[ruby-talk:04502] methods w/ ! giving nil

I have got used to the idea that methods that end in '!' return nil if
nothing changes.  But not all of them do.  Why does array.sort! not behave
like that?  Why should it be different from the array.uniq! method in this
respect?  I wanted to test if a particular method was producing results in
ascending order, and my:

assert_nil(results.sort!) 

failed, when in fact they were in ascending order.  If there is an
underlying reason for some returning nil when nothing changes and some not
then I might be able to know what to expect more often.

Ruby-1.4.4 Sun Sparc Solaris7

	Hugh
	[e-mail]