- From: TeXmacs <address@hidden>
- To: address@hidden
- Subject: Re: Some thoughts and questions about math symbols, multiplication and operators
- Date: Thu, 6 Jan 2022 18:50:52 +0100
Hi Yuliang,
On Thu, Jan 06, 2022 at 10:44:40PM +0800, Yuliang Wang wrote:
>
In math mode if one inputs `ab` with no space between the two letters ,
>
then we get the upright letters `ab`. What is the nature of the string `ab`
>
in this case?
"Words" of several normal letters typed in succession are regarded as
operators by TeXmacs,
which makes it easy to type 'sin x' just by typing 's i n space x'.
(See also section 4.2.2 of The Jolly Writer.)
>
It's not converted to normal text, as I can tell from the status bar. They
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are still separate math symbols, but typed in upright case (but with no
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`math-up` tag). What's the intention of this face-changing behavior? Of
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course, we can insert a * to get what we want and everything is
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semantically correct.
Yes, if you mean 'a times b', then you should type 'a * b'.
>
I don't know about other subjects, but in mathematics one almost never
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represent a variable by more than one letter. So `ab` means nothing but
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`a*b`. Then why not insert a multiplication symbol automatically so that
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the * will not become the most used key when typing math documents. If I
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want an operator named `ab`, then using the "insert operator" is a better
>
way?
Well, 'ab' rarely is meant to be an operator, but many other juxtapositions
of two characters often are.
Also, we want you to make an explicit difference between 'f x' (as f applied
to x, 'f space x') and
'a b' (as a times b, 'a * b').
>
A somewhat related question is the following. There are 3 methods to type
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$\sin x$ in the math mode.
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1. Type `sin x`
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2. Type `\sin x`
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3. Use toolbar icon `op` $\rightarrow$ `Normal`, type `sin`, exit the tag,
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then type space and x. Of course, here we have more options for the
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typeface.
>
The appearance of the three are the same and they are all semantically
>
correct. The 3rd approach has an additional tag 'math-up' around each
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letter in `sin`. Which one is the correct approach?
The recommended way is the first one. The second one is for (ex-)LaTeX users.
The third one is overkill, but can be useful for operators in a different
font,
like a 'sans serif' operator.
Best wishes, --Joris
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