How print top 5 results only?

[Mortimerlol]

Hello to all,

Im sorting a table with ["key"] = value, by (value, key) for do a list with "max. kill numbers - name". This is my code:

function spairs(BangCharKills, order)
    local tkills = {}
    for k in pairs(BangCharKills) do tkills[#tkills+1] = k end
    if order then
        table.sort(tkills, function(a,b) return order(BangCharKills, a, b) end)
    else
        table.sort(tkills)
    end
    local i = 0
    return function()
        i = i + 1
        if tkills[i] then
            return tkills[i], BangCharKills[tkills[i]]
        end
    end
end
for k,v in spairs(BangCharKills, function(BangCharKills,a,b) return BangCharKills[b] < BangCharKills[a] end) do
   print(v.." - "..k)
end

All is OK but now I need show the first 5 results for make a Top5 but I can't resolv positively. I need do similar to:

print(v[1], k[1])
print(v[2], k[2])
print(v[3], k[3])
print(v[4], k[4])
print(v[5], k[5])

Thanks for help !

[SDPhantom]

Here's what I came up with. I completely rewrote the sorting algorithm to support names as keys and kill count as values.

local KillSort;--   Function prototype (Any functions defined with this name will be stored here)
do--    Forced scope enclosure
    local function KVSort(p1,p2)
--      Unpack key/value pairs
        local k1,v1=unpack(p1);
        local k2,v2=unpack(p2);
 
--      Compare values, fallback to keys
        if v1~=v2 then return v1>v2; end
        return k1<k2;
    end
 
    function KillSort(tbl)--    Prototype defined earlier, will store in that upvalue
        local sorttbl={};
        for k,v in pairs(tbl) do table.insert(sorttbl,{k,v}); end-- Scan table and add key/value pairs to sort table
        table.sort(sorttbl,KVSort);--   Sort using our custom function
        return sorttbl;--   Return sorted table (If we returned a reconstructed table with the key/value pairs, they can be randomized again)
    end
end
 
for rank,pair in ipairs(KillSort(BangCharKills)) do
    print(("#%d: %s (%d)"):format(rank,unpack(pair)));--    Print formatted string, "pair" contains a table with key and value
    if rank>=5 then break; end--    Exit loop early if we printed 5 ranks
end

Edit: Fixed KillSort() sorting the wrong table, which surprisingly didn't throw an error trying to unpack() non-tables.

[Mortimerlol]

Originally Posted by SDPhantom Here's what I came up with. I completely rewrote the sorting algorithm to support names as keys and kill count as values. local KillSort;--   Function prototype (Any functions defined with this name will be stored here) do--    Forced scope enclosure     local function KVSort(p1,p2) --      Unpack key/value pairs         local k1,v1=unpack(p1);         local k2,v2=unpack(p2);   --      Compare values, fallback to keys         if v1~=v2 then return v1>v2; end         return k1<k2;     end       function KillSort(tbl)--    Prototype defined earlier, will store in that upvalue         local sorttbl={};         for k,v in pairs(tbl) do table.insert(sorttbl,{k,v}); end-- Scan table and add key/value pairs to sort table         table.sort(tbl,KVSort);--   Sort using our custom function         return sorttbl;--   Return sorted table (If we returned a reconstructed table with the key/value pairs, they can be randomized again)     end end   for rank,pair in ipairs(KillSort(BangCharKills)) do     print(("#%d: %s (%d)"):format(rank,unpack(pair)));--    Print formatted string, "pair" contains a table with key and value     if rank>=5 then break; end--    Exit loop early if we printed 5 ranks end

Thanks for the code ^^ but this return unsorted:

#1: Name 1
#2: otherName 1
#3: oName 3
#4: Namee 2
#5: UnNamed 4

[Kakjens]

I don't see assignment
BangCharKills = KillSort(BangCharKills)
in line 20
Edit. You might also want to use a function for displaying of results, and not to sort during "for" loop but right before it.

[Mortimerlol]

Originally Posted by Kakjens I don't see assignment BangCharKills = KillSort(BangCharKills) in line 20 Edit. You might also want to use a function for displaying of results, and not to sort during "for" loop but right before it.

Thanks u so much!

[Kakjens]

Did that really work? Looking now, I don't see a reason why sorttbl should be updated to reflect the results of sorting.

[SDPhantom]

Originally Posted by Kakjens I don't see assignment BangCharKills = KillSort(BangCharKills) in line 20 Edit. You might also want to use a function for displaying of results, and not to sort during "for" loop but right before it.

The problem with trying to sort BangCharKills directly is that the keys are not numeric. Sorting doesn't work unless they are numeric and sequential. KillSort() returns a sorted list by taking the key/value pairs, enclosing them in tables, and stuffing them as values in the sorting table with sequential indices. As explained before, this is the only way to get sorting to work. The table returned has a completely different structure than the addon uses and is only useful for the for loop, you don't want to overwrite the original table with this.

Originally Posted by Mortimerlol Thanks for the code ^^ but this return unsorted: #1: Name 1 #2: otherName 1 #3: oName 3 #4: Namee 2 #5: UnNamed 4

The problem was in line 16. It's sorting the wrong table, change this to table.sort(sorttbl,KVSort) instead.

[Mortimerlol]

Originally Posted by Kakjens Did that really work? Looking now, I don't see a reason why sorttbl should be updated to reflect the results of sorting.

No, dont work crash my table on savedvariables...

[Kakjens]

SDPhantom, thanks for explanation. That's why I modify the lines 20 and 21 into

local mysortedtable = KillSort(BangCharKills)
for rank,pair in ipairs(mysortedtable) do

Also thought that line 16 is suspicious.
By the way, is sorting of full table required? I naively think that the time required to obtain five top-most results should be smaller.

[SDPhantom]

Trying to track the top X entries would be too much work that would ultimately lead to minuscule if any benefit at all. It's entirely possible that the resulting code would have worse performance. If you really want to help it out, you can upvalue unpack() to cut down on global indexing operations. Aside from using the custom comparison function, Lua's C-side sorting algorithm is fairly efficient. If at all possible, you can gain a lot of performance by not defining one, but situations like these require it.

As far as storing the sorted table into a variable, then giving it to ipairs(). This is an extra step that is unnecessary. You're not using the variable anywhere else in the code and it doesn't offer any benefit.

[Kakjens]

I was thinking about something like partial sort instead of full sort.
About making sorted table into variable - was under wrong impression that KillSort(BangCharKills) would be called during for loop. Seems like lua doesn't recalculate the list in which to loop during the loop.

[SDPhantom]

The example you provided is for C code. While it is possible to emulate this in Lua, the performance impacts of doing so is far different. Not only is Lua code far slower than C, but you don't have the same control over memory usage either.



PS: If you're interested in seeing how for...in works, I suggest reading the last half of this section of the Lua manual.
http://www.lua.org/manual/5.1/manual.html#2.4.5