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

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  • Subject: [mg106553] Re: [mg106529] Re: More /.{I->-1} craziness
  • From: "David Park" <djmpark at>
  • Date: Sat, 16 Jan 2010 06:11:02 -0500 (EST)
  • References: <> <hhhmn8$o9t$> <hhpl28$9lf$> <24942249.1263546688955.JavaMail.root@n11>

I don't use them but what about displayed LaTeX documents? Can you replace
by typing in what you see? What about a YouTube file? Can you replace one
person with another by using two pictures?

If I type in 2 * 3 * 4 and then try to use 2 -> 5, can I claim that I typed
2 in and I should bloody well be able to replace it? Mathematica is a CAS
and MANY things are processed on input and no longer appear in the for they
were entered. It isn't just Complex[a,b].

It's easy to do calculations in Mathematica. You insist on using a method
that doesn't work because it ignores the fact that Mathematica processes
numbers on input. It's a waste of time. There are more interesting places to
'improve' Mathematica. For example, primed and double primed characters are
commonly used in textbooks and papers, but Mathematica does not make it easy
to use them. (I do provide an easy method to use them in Presentations.)
There are many convenient things that can be done, but I -> -I is just a
dead horse.

David Park
djmpark at  

From: AES [mailto:siegman at] 

In article <hhpl28$9lf$1 at>,
 Leonid Shifrin <lshifr at> wrote:

> I stick to my view of replacement rules as being aimed primarily at
> users, or at least as a tool that should be used with much care.  

But on the other hand, innumerable software apps of all varieties and at 
all levels down to the most elementary (e.g., nearly all word 
processors, text editors, graphics programs, spreadsheet programs, email 
programs, and so on) include "Find and Replace" capabilities.

These capabilities frequently have varied options:  
   "Find Next"  "Replace and Find"  "As Word"
   "Start at Top"  "Replace All"  "In Selection Only"
and so on.  Many have optional GREP abilities.


1)  Most any computer user at even a very elementary level knows about 
these tools, rather expects to have them available, and expects them to 
function as they in fact do function.

2)  In particular, they operate (visibly!) on what you see -- not some 
arcane internal representation.

3)  So, if such a novice user goes to Mathematica, it's only to be 
expected that this user will thnik that Mathematica's ReplaceAll should 
function in a similar fashion (and, helpfully, Mathematic's /. operator 
most of the time does function in that way) (sarcasm mode in that 

4)  So why can't Mathematica also have a TextReplace[ ] function, or 
something similar, that would function in that way _on what the user 
sees or has typed (or copied and pasted) into a selected cell_.

Given such a function my input would be Find " I " and replace it
with " (-I) ".

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