In julia you can write subscripts by \_ for variable names. I was wondering if there is anything similar for writing fractions in variable names. Something like \frac{}{} in LaTeX. I understand this may be harder as it takes two arguments. If there is none, I will use /. But in this case I would like to use some enclosures to make clear what is being differentiated. I assume () is not usable? [] or {} would be ok?
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Ronan Boiteau
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ztyh
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I guess `/` is probably not usable either... – ztyh Oct 15 '18 at 16:59
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I guess I can use `\div` – ztyh Oct 15 '18 at 17:02
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can also use `\llbracket` etc, but now its too long defeats the purpose... – ztyh Oct 15 '18 at 17:11
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but i guess its just not possible to fit too much vertically in a single line... – ztyh Oct 15 '18 at 17:12
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just to let you know, I really cherish the freedom in variable naming. Naming variables is becoming a real headache – ztyh Oct 15 '18 at 17:20
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`\not` is probably better than `\div` – ztyh Oct 15 '18 at 17:43
2 Answers
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The subscripts or other non-latin names you see in Julia code are just normal unicodes the same as "regular" names. the LaTeX commands are only a function of Julia REPL to remember and input them.
As for unicode, in principle you can represent some simple fractions like ⁽²⁺ⁱ⁾⁄₍ₛ₊ₜ₎, using the ⁄ (U+2044 Fraction slash) symbol and subscripts and superscripts. The rendering depends on your font, but do not expect a verticle layout in any current fonts.
However, Julia recognizes ⁄ (U+2044 Fraction slash, not the / in your keyboard) as "invalid character" when used along during parsing. The same applies to \not, which can only be used in conjunction with some operators, so it's not an option too.
As for the brackets and the normal /, they are operators and are parsed differently. However, there is an (ugly) way to circumvent this: you can use macros to bypass the parsing and use strings as variable names. For example:
julia> macro n_str(name)
esc(Symbol(name))
end
@n_str (macro with 1 method)
julia> n"∂(2x + 3)/∂x" = 2
2
julia> 2n"∂(2x + 3)/∂x"
4
张实唯
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Hi thank you for the detailed response. Sorry I'm actually not familiar with macros. So how was `n_str` used? – ztyh Oct 17 '18 at 03:49
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Hi, just like in the example, you cound use `n"anything"` as a variable, so the allowed characters extend to anything that can appear in a string, at the cost of `n""` around the name. [this is the document](https://docs.julialang.org/en/v1/manual/metaprogramming/index.html#Non-Standard-String-Literals-1) for non-standard string literals, and you might need to read the whole page to fully understand how macro works. – 张实唯 Oct 17 '18 at 04:18
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I think you might be looking for \diagup (⁄).
Akash Patel
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This does not provide an answer to the question. Once you have sufficient [reputation](https://stackoverflow.com/help/whats-reputation) you will be able to [comment on any post](https://stackoverflow.com/help/privileges/comment); instead, [provide answers that don't require clarification from the asker](https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead). - [From Review](/review/late-answers/34831524) – Ram Chander Aug 18 '23 at 12:45