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is an option for Trace and related functions which specifies when tracing should be switched on.
  • With the setting TraceOn->patt, Trace and related functions do not start tracing until they encounter expressions to evaluate which match the pattern patt. This pattern is also tested against tags associated with the evaluation.
  • Once tracing has been switched off by TraceOff, however, TraceOn will not switch it on again.
  • During the execution of Trace, the settings for TraceOn and TraceOff can be modified by resetting the values of the global variables $TraceOn and $TraceOff.
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