Zugg Software :: View topic - Sorting A Database Record Variable by Value

Wanderer Joined: 20 Oct 2006 Posts: 51

Hello -

I am trying to do as the title suggests. There were a couple of old posts (zMUD era) that regarded this topic, but unfortunately they don't seem to work in CMUD 3.34.

I have a variable @test (type database record) that stores the Key as a name and the Value as a number.

Wizard Joined: 22 Mar 2007 Posts: 2320

No, you cannot sort a database variable by value.

If you want to display the numbers with 2 decimals even if they are zeros, use the %format() function.

GURU Joined: 23 Dec 2000 Posts: 4834 Location: USA

Sorting datarecords by value requires a user function (this is by design, not a workaround). Vijilante might have one, and perhaps there are more in the Package Library, but essentially you would create variables to hold the stinglist returned by %dbkeys() and by %dbvalues(), run a standard sorting algorithm on the %dbvalues() list and taking care to swap the equivalent element positions in both stringlists. Once sorted, you would then #loop through the now-sorted %dbkeys() list and #ADDKEY the appropriate data to the source variable (make sure to blank the source first, or else you lose the sorted result.)

For display purposes, you can use %float(). An alternative would be &x.yf in the %format() function's format string, where x = the number of integer digits and y is the number of decimal digits (there's also an alternative syntax to %format() dedicated to floating-point numbers). If the result amount of decimal places is less than the format string amount (ie, putting 10.2 in &0.4f), the function will automatically include the padding 0's. Which you use depends on where you need the floating-point equivalent of the integer (%float() is generally for calculation, %format() is generally for printing to the screen or assigning to a variable).

Wanderer Joined: 20 Oct 2006 Posts: 51

Two different threads seemed to have done it successfully on the forum, in zMUD. Is this just no longer possible in CMUD..?

Threads:
http://forums.zuggsoft.com/forums/viewtopic.php?t=19800
and
http://forums.zuggsoft.com/forums/viewtopic.php?t=31091

The first one, the guy was looking to do exactly what I'm trying to do. The response was this:

Wanderer Joined: 20 Oct 2006 Posts: 51

Oh sorry Mr. Lofton, I had only seen Rahab's reply before my post. I had never heard of the Package Library before, so I checked the forums and just found the poll and instructions regarding it.. No dice, though, my MUD is somewhat obscure and nothing in All or Core for 'sort database' or similar..

Wizard Joined: 22 Mar 2007 Posts: 2320

Cmud codes database variables in a completely different way than Zmud did, so solutions that worked for Zmud will not work for Cmud. Many things are very different between Zmud and Cmud. It is not that functionality was reduced, since sorting by value was not an intentional feature of Zmud. Database variables in Cmud actually have a lot more functionality than Zmud.

Matt's solution is interesting, and he would know better than I whether it would work. You would have to write your own sorting algorithm, which shifts both elements in the value stringlist and the corresponding elements in the keys stringlist. Actually, here's an alternative method. Follow Matts suggesction except that, rather than create a keys stringlist and a values stringlist, you create a new db variable in which the keys are the old values and the values are the old keys. In otherwords, create a new db variable with the values and keys swapped with each other. Sort that, and then create your final version by swapping keys and values back again.

Sorcerer Joined: 15 Apr 2011 Posts: 809

Internally, database variables use a hash table, so they're not actually sorted at all, by keys or by values. You might notice that when you add a record to a database variable, it doesn't always go to the end of the variable. There's no way you can keep your records in any particular order. The #sort command (or enabling sorting in the package editor) doesn't actually sort the variable internally. CMUD will display the records in sorted order when looking at it in the package editor or with various commands/functions (#showdb, %expanddb, etc), but internally the order is still based on the hash.

So now the solution really depends on what you were trying to do. If your goal was to get it to stay in sorted order by value in the database variable, there's no way you can do that. Matt's suggestion would get you two lists, one with the values in sorted order and the other with the corresponding keys in the same positions, but as soon as you add them to the database variable, the order cannot be guaranteed. Rahab's solution could kinda work, but you'll have the same issue when you try to flip the keys and values back. Even if they are in sorted order when the values are the keys, and you add them to the other variable in the same order as they appear in the sorted one, the order cannot be guaranteed later. If you don't mind working with it flipped though, you could keep it that way. Also, a problem arises if you have any duplicate values. Keys must be unique, while values can be duplicated, so you could end up with a loss of data if you try to make your values keys.

If all you wanted to do was display them in sorted order, not have them stay that way in a database variable, that becomes much easier. Something like this should work (untested):

Wanderer Joined: 20 Oct 2006 Posts: 51

Daern - I don't need to store the keys/values in any form of sorted order, because for my purposes, every time I need to display the information, I can just use the sorting function/alias. The piece you posted works perfectly as long as the values don't end in a decimal. The reason I say this is because values like:

Sorcerer Joined: 15 Apr 2011 Posts: 809

Hmm, how are you adding the numbers to the database? I tried #addkey test Delta 4.0 and it was converted to "4", not "4.", and %format correctly displayed it as 4.00. It sounds like you're somehow adding a string to the database instead of a number, though I couldn't get it to fail with strings at all either (#show %format("&5.2f", %min("4.", 8)) shows 4.00, so both %min and %format must be correctly converting the string to a number). You could try using %float on it (already done in my code below).

If you just want it to display in that format, I wouldn't trust using a string list and #additem, just in case it gets interpreted as a database variable and messes up the order. String concatenation will be safer. If you want to actually use list functions on it, it should work fine with a list too, and I'm sure you can figure out how to convert this.

Wanderer Joined: 20 Oct 2006 Posts: 51

That piece sorts the record correctly and displays it exactly how I was hoping, thank you again. It still locks up CMUD if any of the values are "4." for example, but let me explain what I'm doing and maybe you can help me figure out where I'm making the mistake.

What I'm doing is tracking player's participation in killing a mob on my MUD and giving each a score based on that participation. Player Alpha hits the mob, doing 10 damage let's say, so I trigger off of that message with #ADD's that count the total number of that player's attacks, and in another record variable, the total damage of those attacks. Example:

Trigger:

Sorcerer Joined: 15 Apr 2011 Posts: 809

Aha, I was able to reproduce it with that code! Changing the party_calc alias to #ADDKEY test_calc %1 (%float( @test_score.%1)/%float( @test_total.%1)) seems to fix it (it'll store "4" in test_calc, instead of "4." - the display code above will correctly format it as 4.00 for displaying).

EDIT: if anyone cares, the cause of the infinite loop was with the %ismember(%min($values), $values) line - when "4." was stored in $values, %min would return only "4", and the %ismember would not find it in the $values list.

Wanderer Joined: 20 Oct 2006 Posts: 51

This works exactly as you described! I came across a problem of my own creation though - I plan to use this sorting alias in multiple different places, and for one of them I can't really modify the 'party_calc' equivalent, so although the db record still has the values stored properly (as 4 instead of 4.), as soon as I run it through the sorting alias, it spits out a properly-sorted list that does include the errant decimal, like

Sorcerer Joined: 15 Apr 2011 Posts: 809

Try this:

Wanderer Joined: 20 Oct 2006 Posts: 51

Worked perfectly. Thank you very much for taking so much of your time to help me out here, it is immensely appreciated.