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Re: FindROot and substitutions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg89977] Re: FindROot and substitutions
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Wed, 25 Jun 2008 06:30:36 -0400 (EDT)

On 6/24/08 at 3:20 AM, jeanmarc.gulliet at gmail.com (Jean-Marc Gulliet)
wrote regarding:

>>>g := x z;
>>
>>----------^ You used a semicolon here, so I suppose that you do not
>>understand the difference between SetDelayed and Set.

>The above expression is not a compound expression.

But it is a compound expression. Specifically, it is the
compound expression

g := x z;Null

which is clearly shown by

In[1]:= FullForm@Hold[g := x z;]

Out[1]//FullForm= \
Hold[CompoundExpression[SetDelayed[g,Times[x,z]],Null]]

>SetDelayed does not produce any output.

>Therefore the semicolon is not needed and does not change anything.

>So someone may infer that you do not have a clear idea about about
>the differences between immediate and delayed assignments, which are
>topics of some importance to answer the rest of your original
>question.

Further, there is the only the symbol g appears on the left hand
side of the SetDelayed. I cannot think of any reason why Set
would not be preferred here, adding to the impression there is a
lack of understanding of the differences between Set and SetDelayed.


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