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?
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