Finding non-common elements in two arrays

Alex Tweedly alex at
Sat Nov 5 19:39:32 EST 2005

Bruce A. Pokras wrote:

> The intersect function will return the common elements of two arrays. 
> Is there any array methodology that will return the non-common 
> elements of two arrays? I download a government list each month, and I 
> would like an easy way to spot the records that are either new or 
> changed. Currently, I use a repeat structure to go through the old 
> list line-by-line to see if any lines are not identically found in the 
> new list (using offset), and collect a third list of any lines in 
> which offset=0. After splitting the old and new lists into arrays, an 
> "inverse-intersect" function or equivalent would seem to be a more 
> elegant way of doing this.
> Any ideas?

It's a bit of a faff, so it's arguably not elegant at all, and you'd 
need to do some testing to see if it's faster or not.
(Oh - and the final result still needs cleaning up ....)

> on mouseUp
>     put fld "F1" into t1
>     repeat for each line L in t1
>         put L & TAB & "1" & cr after tA1
>     end repeat
>     split tA1 by CR and TAB
>     put fld "F2" into t1
>     repeat for each line L in t1
>         put L & TAB & "2" & cr after tA2
>     end repeat
>     split tA2 by CR and TAB
>     union tA1 with tA2
>     combine tA1 with CR and TAB
>     filter tA1 with ("*"&TAB&"2")
>     put tA1 into fld F3
> end mouseUp

Alex Tweedly

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