Rationale behind excluding some unicode characters from identifiers

Internals & Design
1

I’m wondering why some Unicode punctuation characters (Open Punctuation Ps, and Close Punctuation Pe) were excluded from variables names (identifiers) in this PR.

julia> ❘u❘ = abs(u)  # allowed, e.g. denote an absolute value
julia> ⟦u⟧ = 1  # why not ? my use case is denoting a jump
ERROR: syntax: invalid character "⟦" near column 1
julia> ⦃u⦄ = 1  # why not ? my use case is denoting an average
ERROR: syntax: invalid character "⦃" near column 1
2

one or more of the following:

  • too subtle
  • too confusing
  • too obscure (user may not know what the heck this symbol means or called or how to type it, sure, can use Julia REPL, but com’on)
2 Likes
3

The slightly more detailed answer is that the parser needs to know whether a character is part of a name or if it is an operator. (e.g. you can’t name a variable a⊂). As such we only add Unicode characters on request.

8 Likes
4

That’s not my question. There are a lot of other Unicode characters that lead to ambiguities and still allowed (difficult to distinguish because of the current font, close to another: it’s the responsibility of the developer to use them sparingly), but I’m interested in knowing why these specific characters were excluded.

5

Thanks, so they might be reserved for future operator usage (conservative choice).
So what would be the criterion for such a request to be accepted ?

6

If they’re added on requests, request it: if it is rejected, you’ll know why!

6 Likes
7

yeah. Just open an issue and if there aren’t problems someone will probably add them to the list.

8

I want to use various fancy brackets as constructors for fancy container objects, so I wouldn’t want them to be in identifiers, just like [](){} aren’t in identifiers.

1 Like
9

Do you have an example ?

10

For example, if I could define

⦃1,2,2,3⦄ == MultiSet([1,2,2,3])
11

I’ve opened [FR] Allow more Unicode characters from `Ps` and `Pe` categories for identifiers · Issue #48885 · JuliaLang/julia · GitHub and Allow more Unicode characters from `Ps` and `Pe` categories for identifiers by t-bltg · Pull Request #48886 · JuliaLang/julia · GitHub, to be discussed.