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I am calling a function that I terminate using TimeConstrained[] if the function doesn't complete in some time. Since TimeConstrained[] returns $Aborted, I thought I will use CheckAbort[] to test for Abort signal and return a default value on failure. I am unable to understand the behavior of CheckAbort[]. As Abort[] and TimeContrained[] both return the special symbol $Aborted, I assumed that the behavior would be the same. I expected the variable test to have value 0 in both cases below but the behavior is confusing. 

test = CheckAbort[TimeConstrained[Pause[2], 1], 0]
test = CheckAbort[Abort[], 0]

Output:

$Aborted
0
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    $\begingroup$ If the abort signal is not crucial for your application, you could also use the third argument to TimeConstrained: TimeConstrained[Pause[2], 1, 0]. $\endgroup$
    – WReach
    Commented Apr 3, 2020 at 4:00
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    $\begingroup$ While the underlying assumption is perfectly reasonable, this issue of TimeConstrained and CheckAbort not being on speaking terms is a long-standing one. I am optimistic that it will finally resolved in the version 12.2 time frame. For now the approach in the response by @Nasser seems like a viable workaround. $\endgroup$
    – Daniel Lichtblau
    Commented Apr 3, 2020 at 16:53

1 Answer 1

Reset to default
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Need to throw an Abort[] when it times out to catch it.

res = CheckAbort[TimeConstrained[Pause[2], 1, Abort[]], 0]

(*0*)

or

res = CheckAbort[TimeConstrained[Pause[2], 1, Abort[]],"Oh no, timed out"]
(* Oh no, timed out *)
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