1D Listから重複項目のみ抽出 v2

AppleScript名：1D Listから重複項目のみ抽出 v2

— Created 2017-11-07 by Takaaki Naganoya
— 2017 Piyomaru Software
use AppleScript version "2.4"
use scripting additions
use framework "Foundation"
–http://piyocast.com/as/archives/4955

property NSCountedSet : a reference to current application’s NSCountedSet

set aList to {1, 2, 3, 4, 1, 2, 3, 4, 5, 1, 2, 3, 1, 2, 3, 8, 10, -2}
set aRes to returnDuplicatesOnly(aList) of me
–>　　{1, 2, 3, 4}

on returnDuplicatesOnly(aList as list)
　　set aSet to NSCountedSet’s alloc()’s initWithArray:aList
　　set bList to (aSet’s allObjects()) as list
　　
　　set dupList to {}
　　repeat with i in bList
　　　　set aRes to (aSet’s countForObject:i)
　　　　if aRes > 1 then
　　　　　　set the end of dupList to (contents of i)
　　　　end if
　　end repeat
　　
　　return dupList
end returnDuplicatesOnly