On 2016-11-08 12:48, Ben Rubinstein wrote:
The point is that in my first pattern, I have outside the loop
assigned column (item) indices to named variables (based on the items
of the first, header, row). In the loop LC then has to locate the
indexed items in an individual data row.
In the first pattern:
repeat for each line tRec in tTSVdata
doSomething item viUserID of tRec, item viUserName of tRec
...
end repeat
The 'item <constant> of tRec' expressions cause the engine to iterate
through tRect until it has found the relevant item. This means that this
single line will be looking through the tRec string twice from the start
- the first time up until the viUserID'd item, the second time up to the
viUserName'd item. The speed of this will largely depend on how large
the item indicies are, and how large tRec is (and where the items fall
in tRec).
If the item indices are small, close and near to the start, and tRec is
small, and you don't use 'item ... of tRec' anywhere else in the loop,
then it will likely be faster than anything else.
In the second pattern, the code which happens to be in a function for
neatness has to create a new empty array, and chunk both the data row
and the header row in order to get column names and values to put into
the array. You can loop over one set of items, but not both, so LC
still has to locate indexed items in at least one case.
put line 1 of tTSVdata into tColumnNames
delete line 1 of tTSVdata
repeat for each line tRec in tTSVdata
put explodeRow(tRec, tColumnNames) into aData
doSomething aData["User ID"], aData["User Name"]
...
end repeat
The performance will largely depend on the implementation of explodeRow
and (as you said subsequently) what
So in short, the function is doing what the inline code is, plus a
whole lot more. (Not to mention that in many cases the 'do something'
code only acts on a subset of the items in each row, whereas the array
of necessity is built out of all of them.) It may or may not be
significantly slower; but it definitely is slower.
Ben
_______________________________________________
use-livecode mailing list
use-livecode@lists.runrev.com
Please visit this url to subscribe, unsubscribe and manage your
subscription preferences:
http://lists.runrev.com/mailman/listinfo/use-livecode
--
Mark Waddingham ~ m...@livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
_______________________________________________
use-livecode mailing list
use-livecode@lists.runrev.com
Please visit this url to subscribe, unsubscribe and manage your subscription
preferences:
http://lists.runrev.com/mailman/listinfo/use-livecode
