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Re: TraceInternal and OptionQ

  • To: mathgroup at
  • Subject: [mg8995] Re: [mg8949] TraceInternal and OptionQ
  • From: Allan Hayes <hay at>
  • Date: Tue, 7 Oct 1997 03:35:41 -0400
  • Sender: owner-wri-mathgroup at

tburton at (Tom Burton)
[mg8949] TraceInternal and OptionQ
remarks on the lack of documentation of TraceInternal and OptionQ  
and aks why use ___?OptionQ in preference to ___Rule.

(1) Yes, they could be better documented, but we can get at them:

{MatchLocalNames -> True, TraceAbove -> False,
  TraceBackward -> False, TraceDepth -> Infinity,
  TraceForward -> False, TraceInternal -> Automatic,
  TraceOff -> None, TraceOn -> None,
  TraceOriginal -> False}

"TraceInternal is an option for Trace and related functions which,  
if True or False, specifies whether to trace evaluations of  
expressions generated internally by Mathematica. The intermediate  
Automatic setting traces a selected set of internal evaluations  
including Messages and sets or unsetsof visible symbols."

"OptionQ[e] returns True if e can be considered an option
or list of options, and False otherwise."

(2) As for ___?OptionQ compared with  ___Rule

 a ->b, a:>b and  {a ->b, a->b} both match the first but not the second 

I recommend ___?OptionQ

Allan Hayes
hay at
voice:+44 (0)116 2714198
fax: +44 (0)116 2718642
Leicester,  UK

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