From: oadartse@... (Osuka)
Date: 2003-07-03T08:24:37+09:00
Subject: Re: Sorting a Hash

Brian Candler <B.Candler@pobox.com> wrote in message news:<20030701211409.GA66745@uk.tiscali.com>...
> On Wed, Jul 02, 2003 at 01:50:30AM +0900, Osuka wrote:
> > > If you want to sort it by the numeric value, then you can pass in an
> > > explicit block which shows how to compare the values:
> > > 
> > >   myhash.sort {|x,y| x[1] <=> y[1]}
> > > 
> > > => [["Ayumi Hamasaki", 1], ["L'Arc~en~ciel", 1], ["Two-Mix", 1],
> > >     ["Shazna", 2], ["Zone", 2]]
> > > 
> > > (you can see all the 1's come before the 2's)
> > 
> > Arrg I did tried this and the to_a approach but i forgot something way
> > too simple! if myhash.sort {|x,y| x[1] <=> y[1]} does return the
> > sorted array but doesn't actually affects the given array so I have to
> > assign the returned value to the hash I'm using, how come I miss it!!!
> > all the problem was here!!
> 
> Of course, the result of the sort is an array, not a hash. There's no point
> trying to put the elements back into a hash, because a hash is _unordered_
> by definition. Effectively they would end up in a random order again.
> 
> > Yes I want it sorted by descending values not alphabetical
> > [["Shazna", 2],["Zone", 2],["Ayumi Hamasaki", 1], ["L'Arc~en~ciel",
> > 1], ["Two-Mix", 1]]
> 
> Ah OK. Actually quite a nice solution is:
> 
>     myhash.sort { |x,y| y[1] <=> x[1] }
> 
> or even better,
> 
>     myhash.sort { |x,y| y.reverse <=> x.reverse }
> 
> The 'reverse' swaps x[0]/x[1], so it sorts by the number before sorting by
> the name. Using y...<=>...x gives a sort in reverse order. So this will
> group together all the entries by number, sorted in reverse numeric order,
> and within groups it will sort by reverse alphabetic order.
> 
> If you want reverse numeric and forward alphabetic, you can get a bit more
> imaginative with the contents of the comparison function:
> 
>     myhash.sort { |x,y|
>       cmp = y[1] <=> x[1]
>       if cmp != 0
>         cmp
>       else
>         x[0] <=> y[0]
>       end
>     }
> 
> => [["Shazna", 2], ["Zone", 2], ["Ayumi Hamasaki", 1], ["L'Arc~en~ciel", 1],
> ["Two-Mix", 1]]
> 
> Cheers,
> 
> Brian.

Yes I mistyped there!! I tried to mean the array returned, 'cos the
hash its no more after a sort, I should be more careful with those
words. And thanks a lot Brian I didn't thought of doing an
alphabetical(as secondary rule) sort after the numerical, I guess that
was coming even in the example that I gave on what I wanted I did it
like that.Now it all works and as a little exercise I turned it into a
class(a bit of overkill but...gotta learn)