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MathGroup Archive 2004

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Re: undocumented function StringQ

  • To: mathgroup at smc.vnet.net
  • Subject: [mg47804] Re: undocumented function StringQ
  • From: Harold.Noffke at wpafb.af.mil (Harold Noffke)
  • Date: Tue, 27 Apr 2004 04:47:43 -0400 (EDT)
  • References: <c6d8dd$jh6$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

$Version "5.0 for Microsoft Windows [2000] (November 18, 2003)"

Ingolf:

Robert Villegas' original code ...

	Block[{$Urgent = {}},   

          Select[Names["System`*"], 

            (Information[#]; Not @ StringQ[

              MessageName @@ Append[ToHeldExpression[#], "usage"]

            ])&

          ]

        ]

can be revised to remove Information[#] and $Urgent={}.  This produces
a Block which gives identical results ...

	Block[{}, Select[ Names["System`*"],
	    (!StringQ[MessageName @@ Append[ToHeldExpression[#],"usage"]])& ]
	]

It is use of the $Urgent={} expression which puzzles me.  I don't see
what the programmer's intent is in doing this.  MathBook says ...

	$Urgent gives the list of files and pipes to which urgent output
	from Mathematica is sent.

	In[117]:=
		$Urgent//FullForm 
	Out[117]//FullForm=
		List[OutputStream["stdout",1]]
		
In normal programming, what is the $Urgent={} expression supposed to
provide for us?  How is it supposed to be used?

Thanks.
Harold


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