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Re: Releasing several Holds simultaneously

• To: mathgroup at smc.vnet.net
• Subject: [mg82358] Re: Releasing several Holds simultaneously
• From: David Bailey <dave at Remove_Thisdbailey.co.uk>
• Date: Thu, 18 Oct 2007 04:56:41 -0400 (EDT)
• References: <ff1po5$90n$1@smc.vnet.net>

Andrew Moylan wrote:
> Hold[a := Hold[1]]
> 
> How can I release both of these Holds (and thus execute a:=1)
> simultaneously?
> 
> ReleaseHold[%] doesn't work; it evaluates a := Hold[1] before the other hold
> is removed.
> 
> % /. Hold[x_]:>x does the same thing, because /. only matches once per part.
> 
> 
Try

Hold[a := Hold[42]] /. Hold -> Identity

David Bailey
http://www.dbaileyconsultancy.co.uk