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MathGroup Archive 2007

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Re: Evaluation question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80340] Re: Evaluation question
  • From: David Bailey <dave at Remove_Thisdbailey.co.uk>
  • Date: Sat, 18 Aug 2007 05:32:44 -0400 (EDT)
  • References: <fa13jg$nua$1@smc.vnet.net>

Yaroslav Bulatov wrote:
> Abs[-1 - 2 E - E ^2 + (1 + E)^2]
> Evaluate[%]
> 
> Why is the "N::meprec" message only printed once?
> 
> 
Although Mathematica appears to evaluate expressions from scratch, for 
performance reasons, it keeps information that lets it know that an 
expression cannot change by further evaluation. This information is 
quite subtle, because if an expression contains a variable, it 
recognises that it needs to re-evaluate if the variable is given a value.

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


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