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Re: Unevaluated

• To: mathgroup at smc.vnet.net
• Subject: [mg44472] Re: [mg44465] Unevaluated
• From: Anton Antonov <antonov at wolfram.com>
• Date: Wed, 12 Nov 2003 08:01:23 -0500 (EST)
• References: <200311110055.TAA25198@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hans-Peter Kunzle wrote:

>Hello,
>
>I was trying to make a function like 'tPrint[x___]' that would act
>like Print if some global variable Testing was True and do nothing
>if Testing was False. This would allow me to simply add or delete
>the 't' to individually turn on or off some tracing. It would
>be easier than to comment or uncomment the Print statements each
>time.
>
>But when I tried
>
>	tPrint[Unevaluated[x___]]:= If[Testing,Print[x]]
>
>I found, using TracePrint, that 'x' gets evaluated each time whether
>or not Testing is True.
>
>Maybe I do not understand properly how Unevaluated operates.
>Is there a way to do what I want?
>
>Any help is appreciated.
>
>Hans
>  
>
If I understand your question correctly, using the attribute HoldAll 
will do the job.

--
Anton Antonov
Wolfram Research, Inc.

• References:
  • Unevaluated
    • From: Hans-Peter Kunzle <hp.kunzle@ualberta.ca>