Check

Check[expr,failexpr]

evaluates expr, and returns the result, unless messages were generated, in which case it evaluates and returns failexpr.

Check[expr,failexpr,{s1::t1,s2::t2,…}]

checks only for the specified messages.

Check[expr,failexpr,"name"]

checks only for messages in the named message group.

Details

  • Check has attribute HoldAll.
  • Check does not test for messages that have been switched off using Off, or by uses of Quiet that occur inside it.
  • The operation of Check is not affected by being enclosed inside Quiet.
  • In Check[expr,failexpr,"name"], possible named message groups are given by $MessageGroups.
  • Explicit message names of the form s::t can be mixed with named message groups.

Examples

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Basic Examples  (2)

Return err when a message is generated:

In[1]:=
Click for copyable input
Out[1]=
In[2]:=
Click for copyable input
Out[2]=

Check only for specific messages:

In[1]:=
Click for copyable input
Out[1]=
In[2]:=
Click for copyable input
Out[2]=

Applications  (1)

Properties & Relations  (1)

Introduced in 1988
(1.0)
|
Updated in 2008
(7.0)