Sorting Arrays
Alex Tweedly
alex at tweedly.net
Thu Aug 10 15:29:52 EDT 2023
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.
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