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Failsafe[f][x1,x2,…]

returns f[x1,x2,…] if none of the xi is considered a failure, and the first failing xi otherwise.

Failsafe[f,test][x1,x2,…]

returns f[x1,x2,…] if test[x1,x2,…] gives True, and Failure[…] otherwise.

Failsafe[f,test,failf][x1,x2,…]

returns failf[x1,x2,…] if test[x1,x2,…] does not give True.

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Failsafe

Failsafe[f][x1,x2,…]

returns f[x1,x2,…] if none of the xi is considered a failure, and the first failing xi otherwise.

Failsafe[f,test][x1,x2,…]

returns f[x1,x2,…] if test[x1,x2,…] gives True, and Failure[…] otherwise.

Failsafe[f,test,failf][x1,x2,…]

returns failf[x1,x2,…] if test[x1,x2,…] does not give True.

Details

Examples

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Basic Examples  (2)

Apply a failsafe version of a function:

Wolfram Language code: Failsafe[f][x]

The failsafe version returns the argument unchanged when it is a failure:

Wolfram Language code: Failsafe[f][$Failed]

Make a failsafe version of Sqrt that only applies to positive numbers:

Wolfram Language code: Failsafe[Sqrt, Positive] /@ {1, 2, -10, Missing[]}

Scope  (2)

Map a failsafe function over a list, leaving existing failures unchanged:

Wolfram Language code: Failsafe[f] /@ {1, 2, 3, Missing["NotAvailable"], 6, $Failed, 10}

Failsafe functions can be applied to multiple arguments:

Wolfram Language code: Failsafe[f][1, 2, 3]

By default, it fails if any arguments are considered a failure:

Wolfram Language code: Failsafe[f][1, Missing[], 3]

test and failf are applied to all arguments at once:

Wolfram Language code: Failsafe[Divide, #2 != 0&, g][2, 2]
Wolfram Language code: Failsafe[Divide, #2 != 0&, g][2, 0]

Applications  (1)

Make a version of Divide that returns Missing[] when its second argument is 0:

Wolfram Language code: Failsafe[Divide, #2 != 0&, Missing[]&]@@@{{2, 2}, {4, 5}, {7, 0}, {3, 4}, {0, 0}, {1, 2}}

Properties & Relations  (4)

Failsafe[f][x1,x2,…] returns the first xi that fails:

Wolfram Language code: Failsafe[f][1, $Failed, 2, Missing["NotAvailable"]]

Failsafe[f,test][x1,x2,…] applies test to all the xi simultaneously:

Wolfram Language code: Failsafe[f, EchoEvaluation[UnsameQ[##]]&][x, y, z]
x=!=y=!=z
True

Failsafe[f,test,failf][x1,x2,…] applies failf to all the xi simultaneously:

Wolfram Language code: Failsafe[f, False&, g][x, y, z]

Failsafe can often be approximated with Confirm and Enclose:

Wolfram Language code: {Failsafe[f][x], Enclose[f[Confirm[x]]]}
Wolfram Language code: {Failsafe[f][$Failed], Enclose[f[Confirm[$Failed]]]}
Wolfram Research (2025), Failsafe, Wolfram Language function, https://reference.wolfram.com/language/ref/Failsafe.html.

Text

Wolfram Research (2025), Failsafe, Wolfram Language function, https://reference.wolfram.com/language/ref/Failsafe.html.

CMS

Wolfram Language. 2025. "Failsafe." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Failsafe.html.

APA

Wolfram Language. (2025). Failsafe. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Failsafe.html

BibTeX

@misc{reference.wolfram_2026_failsafe, author="Wolfram Research", title="{Failsafe}", year="2025", howpublished="\url{https://reference.wolfram.com/language/ref/Failsafe.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_failsafe, organization={Wolfram Research}, title={Failsafe}, year={2025}, url={https://reference.wolfram.com/language/ref/Failsafe.html}, note=[Accessed: 12-June-2026]}