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How to check whether application is already active?

The following piece of code checks whether the application is already active:

duble_check(TaskWin) :-
ScrWin = cast(window,win_GetAttrVal(Win,attr_screen_window)),
WINLIST = win_GetChildWindows(ScrWin),
WinText = win_GetText(TaskWin),
member_nd(OtherTaskWin,WinList),
OtherTaskWin<> TaskWin,
TaskWinText = win_GetText(OtherTaskWin),
TaskWinText = WinText,
!,
win_BringToTop(OtherTaskWin),
win_Destroy(TaskWin).
duble_check(_).