Sorting Arrays

[Alex Tweedly]

On 09/08/2023 00:15, Bob Sneidar via use-livecode wrote:
> Has anyone come across a need to sort a numbered array by the values of the different keys? Here you go.

Absolutely I have needed that quite often now. I tend to use sequences 
(numbered arrays) often - maybe too often.

Up until now I've just done the sorting in the "traditional" way (i.e. 
using multiple "sort" commands), like

>    put seqAsLines(sQ2) into tKeys
>    sort lines of tKeys numeric by sQ2[each]["anumber"]
>    sort lines of tKeys by sQ2[each]["thecategory"]
>    rebuildSeq sQ2, tKeys
(the functions seqAsLines and rebuildSeq are included in the code 
snippet below).

But I really like your idea of having a handler that can be given 
multiple sort keys, and just does it all, so I took a detailed look.

First - a couple of little bugs for you.

> Keep in mind that there is no error checking so I have no idea what would happen if you provided a sort key that didn’t exist in the array.
>
> on sortNumberedArray @pArrayDataA, pSortKeys
>           switch
>              case tKeyWord is among the items of "asc,ascending,desc,descending"
>                 put tKeyWord into tSortKeysA [i] ["sortorder"]
>                 break
>              case tKeyWord is "International,Numeric,datetime,text,binary"
'is' should be 'is among the items of'
>                 put tKeyWord into tSortKeysA [i] ["sorttype"]
>                 break
>              default
>                 put word 1 to x of tSortIndex into tSortKeysA [i] ["sortvalue"]
>           end switch
>        end repeat
>     end repeat
>     

Secondly, not sure if it's a bug or simply a limitation - the code fails 
if one of the array keys to use for sorting is one of 
"asc,desc,numeric,...".


And - overall, an alternate suggestion. I think your way is a bot complex.
Combining my "traditional" way as above, and your example, I came up 
with a  simpler way to do the same thing:

> on simpleSortNumberedArray @pArrayDataA, pSortKeys
>    local tKeys, tSeq, tOneSortKey, tSortCommand
>    put seqAsLines(pArrayDataA) into tKeys
>    repeat with I = the number of items in pSortKeys down to 1
>       put item I of pSortKeys into tOneSortKey
>       put "sort lines of tKeys" && word 2 to -1 of tOneSortKey && \
>             "by pArrayData[each][" && word 1 of tOneSortKey && "]" 
> into tSortCommand
>       do tSortCommand
>    end repeat
>    rebuildSeq pArrayDataA, tKeys
> end simpleSortNumberedArray
>
> function seqAsLines pSeq
>    local tRes
>    repeat with i = 1 to the number of elements in pSeq
>       put i & CR after tRes
>    end repeat
>    return tRes
> end seqAsLines
>
> command rebuildSeq @pSeq, pList
>    local tResQ, tCount
>    repeat for each line L in pList
>       add 1 to tCount
>       put pSeq[L] into tResQ[tCount]
>    end repeat
>    put tResQ into pSeq
> end rebuildSeq
This is simpler and, I think, easier to understand. And it's certainly 
much faster: takes 89 msec for my test case rather than 3416 msecs.

Alex.