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RE: Seemingly strange behavior - HoldForm and Evaluate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68136] RE: [mg68109] Seemingly strange behavior - HoldForm and Evaluate
  • From: "David Park" <djmp at earthlink.net>
  • Date: Tue, 25 Jul 2006 04:01:40 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

HoldForm has only one argument and you need to evaluate that.

a = 2; b = 3;
HoldForm[Evaluate[a + b]]
5

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/ 

From: Bharat Bhole [mailto:bbhole at gmail.com]
To: mathgroup at smc.vnet.net


I came across this when answering one of the queries posted on this forum.

If I write

(1)
In: a = 2;
     HoldForm[a]

Out: a

(2)
In: a=2;
     HoldForm[Evaluate[a]]

Out: 2

(3) In: a=2;
         b=3;
         HoldForm[Evaluate[a] + Evaluate[b]]

Out: Evaluate[a] + Evaluate[b]



Example 2 seems to suggest that Evaluate works as expected, i.e., it
evaluates the expression assigns value 2 despite the HoldAll attribute of
HoldForm. However, in example 3, evaluate does not function as expected, or
may it does, but I do not understand why a and b are not assigned there
values.

Thanks,
Bharat.




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