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HoldForm[0] (???)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113898] HoldForm[0] (???)
  • From: kj <no.email at please.post>
  • Date: Wed, 17 Nov 2010 05:30:54 -0500 (EST)


I came across this puzzling bit while inspecting a trace:

In[416]:= Quiet[InputForm[Trace[First[]][[2, 1]]]]

Out[416]//InputForm=
HoldForm[Message[First::argx, HoldForm[First], HoldForm[0]]]

That HoldForm[0] mystifies me.  It looks completely unnecessary.
What harm could come from evaluating 0 in this case?  It can't
possibly be slower than "evaluating" HoldForm[0].

By the same token, HoldForm[First] looks almost as unnecessary.
(I suppose that there could be some bizarre situation in which
First won't evaluate to First, but I have a hard time imagining
it.)

kj

PS: FWIW, First::argx gets interpreted as General::argx, which
evaluates to

"`1` called with `2` arguments; 1 argument is expected."


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