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Re: More /.{I->-1} craziness

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  • Subject: [mg106147] Re: More /.{I->-1} craziness
  • From: David Bailey <dave at>
  • Date: Sat, 2 Jan 2010 05:09:15 -0500 (EST)
  • References: <hhf5s3$h4o$> <> <hhkj5p$534$>

Murray Eisenberg wrote:
> "One of the first things you learn...."  Hmm... Where exactly in the 
> Documentation Center would one be expected to learn about replacement 
> rules -- and is that really one of the first things you learn there?
> When I ask this, I try to place myself in the position of somebody who 
> has NOT come to Mathematica with a long experience of previous versions 
> and their associated documentation.
> David Bailey wrote:
>> .... One of the first 
>> things you learn about replacement rules is that they operate 
>> structurally, and the structure of -I (FullForm[-I]) is Complex[0,-1], 
>> which clearly does not match FullForm[I], which is Complex[0,1] - end of 
>> story!

I know what you mean - but AES is not exactly a Mathematica newbie! I 
suppose what I meant to say, was that when I gave introductory 
Mathematica courses, I covered the pitfalls of replacement rules on day one!

It seems to me that the documentation post-6.0 leaves a lot to be 
desired, and with the constant tidal wave of new functionality arriving 
in Mathematica, this is something that becomes ever more serious.

Incidentally, the main reason why I stopped giving courses and 
concentrated on consultancy, was that I felt that nobody - certainly not 
me - could really do justice to the functionality available.

David Bailey

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