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Why does the command 'HoldForm' appear for the derivative of the 2nd function?

Vincent Renaud
Posted 2 years ago

I'm aware of problems with subscripted symbols but in this example, the use of Symbolize fix the problem for the function ur. Then, with the function f (exactly the same definition as ur !) Mathematica returns HoldForm'[function f] after the solution. I don't understand why both responses are different.

Attachments:
testHoldForm.nb
POSTED BY: Vincent Renaud
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Hans Milton
Hans Milton
Posted 2 years ago

To see string quotes in output cells you could use a simple stylesheet. Save the attached stylesheet to your PC. Then load it from an open notebook:

enter image description here

The stylesheet sets the option ShowStringCharacters to True for output cells. It is False by default.

Attachments:
Stylesheet strin...nb
POSTED BY: Hans Milton

Thank you for alerting me to the ShowStringCharacters option. I have added to my personal style sheet. I still object to the design choice of setting it to False by default.

There remains the probem of the multiple-click (or extend selection) to select a string. When the string is not purely alphanumerical, as in "a b", double-click will select only part of the text, triple-click will select everything and the quotes. There seems to be no way to select only the content of the string, without the quotes. This is in contrast with what happens, for example, with {a, b}. Double-click will select the content without the brackets.

But maybe it is too late to change this basic editing behaviour.
POSTED BY: Gianluca Gorni

The FrontEnd interface can hide important information, specially in the output and in Traditional Form. The main example is that the output of strings hides the "" quotes in the output:

In[268]:= a - "a"

Out[268]= -"a" + a

Here the output in them front end looks identical to -a+a.

If I triple-click on the output of "a&b" to select what appears as a&b without quotes, and then paste it I get the quotes. If I double-click the ouput of "abc" to select, then copy and paste it, I do not get quotes (for that I need a triple-click). There is no visual indication of quotes: sometimes they get copied, sometimes not.
POSTED BY: Gianluca Gorni

I realized now that Symbolize is very tricky indeed. If I type Subscript[r,2] literally, it will not get symbolized. In the following the subscript is typed once with ascii Subscript[r,2] and next with two-dimensional input:

In[1]:= << Notation`
Symbolize[NotationTemplateTag[Subscript[r, 2]]]
ClearAll[r];
Subscript[r, 2] - Subscript[r, 2]

Out[4]= -Subscript[r, 2] + Subscript[r, 2]
Attachments:
18465210.nb
POSTED BY: Gianluca Gorni
Vincent Renaud
Vincent Renaud
Posted 2 years ago
POSTED BY: Vincent Renaud

If you take

f[r, \[Theta]] // InputForm

you will see that there is a hidden HoldForm inside. How did you type the expression?
POSTED BY: Gianluca Gorni
Vincent Renaud
Vincent Renaud
Posted 2 years ago

So this is due to an unfortunate Copy-Paste, I don't see any other explanation because, of course, I've never typed this. Thank you very much for your answer : now I know the importance of //InputForm !!!
POSTED BY: Vincent Renaud
Vincent Renaud
Vincent Renaud
Posted 2 years ago
POSTED BY: Vincent Renaud
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