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How to detect 'bad' characters in expressions in the notebook?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113346] How to detect 'bad' characters in expressions in the notebook?
  • From: "Nasser M. Abbasi" <nma at 12000.org>
  • Date: Sun, 24 Oct 2010 06:07:00 -0400 (EDT)
  • Reply-to: nma at 12000.org

Experts;

I copied a Mathematica expression from a PDF file to a Mathematica 
notebook (by using the mouse, selected the expressions and pasted it 
into a new cell in the notebook).

The expression looked fine, nothing that I can see wrong with it. But 
when I execute it, Mathematica complained with an error message that did 
not make any sense given what I have on the screen.

I knew that there was some problem with the copy, because when I typed 
the same exact command below it, it worked with no errors.

But looking at the screen, both what I copied and what I typed, are 
exactly the same. Absolutely exactly the same expressions looked the 
same on the screen as you can see yourself by looking at the screen 
shot, link below.

But when I converted the commands to inputForm to compare the copied 
command with the I typed, I saw the difference.

In the PDF copied command, it had

PlotRange->{}

The arrow was the problem.

For some reason, it remained of some encoding which did not match 
Mathematica's own -> that one enters by typing dash followed by > which 
then Mathematica converts automatically to a nice solid one glyph ->.

Here is an image showing the problem
http://12000.org/tmp/hidden_stuff/image.png

And here is the notebook
http://12000.org/tmp/hidden_stuff/hidden.nb

So, my question: was there a way I could have asked Mathematica to 
highlight such characters as being ones which it did not recognize?

This would have saved much time.

I have had such problems before, where what I look at in the notebook, 
is not what I think it is. The above is an example.

I guess my lesson for today: next time I copy something from a PDF file 
or other source to the notebook, I better examine each character in 
inputForm before using it even if it did look OK on the screen.

Sounds like so much fun.

--Nasser




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