Re: Push and Pop on a Priority Queue appears to change nature of Array

Thank you much.  Sorry about the wordiness but I was not sure where the
source of the problem was and didn't want to leave out what might have been
the cause.  The brackets were the last thing I would have suspected.  So
also thank you for the instruction in Ruby.

I've have tried your suggestion and removed the second sets of brackets, and
it works now.  I should point out that the command p removed_entry[3] did
not put brackets around the value in the display.  So I would not have known
what the problem was using the p command.  I had not tried the p
removed_entry[3][0] display.

Again, your helpfulness is greatly appreciated.  Working with
multi-dimensional arrays is tricky in Ruby for programmers new to the
language.

Now I can move beyond that logjam.  Ruby program to solve 8-puzzle is 90%
completed.  I'm sure that many parts could be more efficiently written if I
understood some of the finer capabilities of Ruby.  And I eventually will.
I'm persistent.

No Sam

On Sun, Sep 27, 2009 at 2:36 AM, John W Higgins <[e-mail]> wrote:

> On Sat, Sep 26, 2009 at 10:38 PM, Mason Kelsey <[e-mail]
> >wrote:
>
> > I'm stumped.  Worked on this problem for over three hours.  I created an
> > array:
> > current_state = [3, 1, 6, 5, 2, 0, 4, 7, 8]
> > and
> > puts "Current_state.index(0) = " + current_state.index(0).to_s  displays
> > a 5, as would be expected
> > puts "Length of current_state array = " + current_state.length.to_s
> > displays a 9, as expected
> >
> >
> First, not trying to be an idiot or anything but you are using WAY too many
> words mixed in with your code here to describe your issue. Keeping things
> simple but descriptive will get you much more assistance because it's
> easier
> to read.
>
> Lets take the 3 lines above. This would be much simpler
>
> current_state = [3, 1, 6, 5, 2, 0, 4, 7, 8]
> p current_state #=> [3, 1, 6, 5, 2, 0, 4, 7, 8]
>
> note the #=>, this is the nicer way of describing what you get back from a
> line - keeps it simple and less "wordy".
>
> Also, using p or even better doing a require 'pp' and using pp gives you
> better information when debugging because it will return more "object"
> information as you'll see below.
>
>
>
> > I defined a Priority Queue to create an ascending queue with:
> > open_queue = PQueue.new(proc{|x,y| x[0][0]<y[0][0]})
> >
> > Then I push it into the Priority Queue with four other objects:
> > open_queue.push([[hv], [node_level], [direction_of_prior_move],
> > [current_state], [parent_node]])
> >
> >
> If you can make your problem simpler - please try to do so. If the priority
> queue is causing you a problem then try your work just adding your single
> array into the queue - again it's simpler and is easier for folks to
> duplicate. We have no idea what the other elements might contain, nor does
> it really matter.
>
> Now that I've been branded the village idiot, let's solve your problem.
> It's
> actually simple, you've added arrays of arrays to your queue as opposed to
> an array of your elements. The inner []'s are not necessary and are what is
> messing you up.
>
> open_queue.push([hv, node_level, direction_of_prior_move, current_state,
> parent_node]) # correct call
>
> As to why you would have been better with p instead of puts - well if you
> did the following the error would have been much easier to see (assuming
> the
> use of your original code).
>
> removed_entry = open_queue.pop
>
> p removed_entry[3] #=>[[3, 1, 6, 5, 2, 0, 4, 7, 8]]
> p current_state #=> [3, 1, 6, 5, 2, 0, 4, 7, 8]
>
> current_state was the original entry you pushed in from above - note the
> lack of the second [] around the original array. That may not have given
> you
> the immediate answer - but if you had given that as your problem "why are
> there an extra set of brackets around my value" or "why is my value wrapped
> in an array" - it would have made the question much easier :)
>
> One other small last tip - when you're debugging - don't be "cute" and try
> to dig deeper then you need to start the analysis - don't worry about what
> the index of 0 is inside your array - examine the array itself. For
> example,
> again assuming your original code the following might have been much more
> help to you.
>
> p removed_entry[3] #=>[[3, 1, 6, 5, 2, 0, 4, 7, 8]]
> p removed_entry.class #>Array
> p removed_entry[3].length #=>1 ???huh???
> p removed_entry[3][0] #=>[3, 1, 6, 5, 2, 0, 4, 7, 8] ???huh??
> p removed_entry[3][0].class #>Array ???huh???
>
> Certainly if that didn't start leading you to examine the extra []'s -
> again
> it would have made your question much simpler to look at and diagnose.
>
> So now that I've spent wayyyyy too many words myself - the bottom line is
> that you don't want to wrap each element inside an array - get rid of the
> []'s around each element and you'll be in business.
>
> John
>