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Catch

Catch[expr]
returns the argument of the first Throw generated in the evaluation of expr.
Catch[expr, form]
returns value from the first Throw[value, tag] for which form matches tag.
Catch[expr, form, f]
returns f[value, tag].
  • Catch[expr, ...] always returns the value of expr if no Throw was generated during the evaluation.
  • form can be any expression, and is often a pattern.
  • tag in Throw[value, tag] is re-evaluated every time it is compared to form.
EXAMPLESCLOSE ALL
Basic Examples   (3)
Exit to the enclosing Catch as soon as the Throw is evaluated:
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Define a function that can "throw an exception":
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The result of the Catch is just what is thrown by Throw:
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Use Throw to exit a loop when a criterion is satisfied:
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