On Wed, 1 Jun 2005 12:33:42 +0200
Alan Barrett <apb@cequrux.com> wrote:

[snip]
> >  .It Cm \&:O
> >  Order every word in variable alphabetically.
> > +.It Cm \&:Or
> > +Reverse words in variable from head to tail.
> 
> It's not clear whether "head to tail" refers to the original order
> or alphabetical order.  So I'd say something like "Order words in
> variable in reverse alphabetical order."  Possibly also mention that
> ${variable:Or} is equivalent to ${variable:O:[-1..1]}.

This is a not. It really just reverts word list from head to tail as it
':[-1..1]' did :-/

Unfortunately, I haven't found this feature before and now I doesn't
see any reason to left it in code, even as shorten ':O:[-1..1]'. Did
you?

> > +.It Cm \&:Ox
> > +Randomize words in variable. The results will be different each
> > +time you are referring to the modified variable; use the assignment
> > +with expansion
> > +.Pq Ql Cm \&:=
> > +to prevent such behaviour.
> 
> Perhaps this explanation would benefit from an example?

Added to man page.

> > If randomization will be done on unsorted
> > +source sequence, it may produce an alphabetically ordered result;
> > +to avoid this explicitly sort the source, and then randomize it as
> > +.Ql Cm \&:O:Ox .
> 
> It should be expected that shuffling the words will ocasionally produce
> ordered output.  That's part of the nature of random shuffling.  There
> should be no need to try to prevent it.  Trying to prevent ordered otput
> from a random process actually reduces the randomness of the process.
> So I would remove this sentence frmo the man page.

OK. Done.

> >   * Input:
> >   *	str		String whose words should be sorted
> > + *	otype		How to order: (s)ort, (r)everse, intermi(x) 
> 
> The term "intermix" doesn't tell me that it means "random".  I suggest saying
> "(x) random".

Fixed.

> > +	    /* intermixed variable should return different values each time */
> > +	    gettimeofday(&rightnow, NULL);
> > +	    srandom(rightnow.tv_sec + rightnow.tv_usec);
> 
> I don't think there's any gain from calling srandom() more than once per
> program execution.

Improved, thanks.

> > +	    for (i = 0; i < ac; i++) {
> > +		    ai[i].rnd = random();
> > +		    ai[i].avi = av[i];
> > +	    }
> 
> I suggest using the shuffling method used in the get_shuffle() function
> in src/usr.bin/shuttle/shuffle.c.  It has some good properties proved by
> Knuth.

Already done after some private discussion with Greg Troxel. I've used
just the same variant as in shuffle, but without seen it before :-)

--
Mishka.