On Fri, Apr 9, 2021 at 6:09 PM Stéfane Fermigier <sf@fermigier.com> wrote:
>
> I think the best alias for "empty set" would be the Unicode character "Empty set" or U+2205, i.e. "∅".
>
> Alas, it's not a valid identifier in Python:
>
> >>> ∅ = set()
> File "<stdin>", line 1
> ∅ = set()
> ^
> SyntaxError: invalid character '∅' (U+2205)
>
> It works with the similarly looking "ϕ" or 'GREEK PHI SYMBOL' (U+03D5)
>
> >>> ϕ = set()
> >>> ϕ.union({1,2})
> {1, 2}
>
> But it's less than ideal.
>
> I think it's an error from the Unicode standard to list the empty set as a "Mathematical Operator" (https://en.wikipedia.org/wiki/Mathematical_operators_and_symbols_in_Unicode#Mathematical_Operators_block) and not as a
> "Letterlike Symbol" like ℝ or ℕ (https://en.wikipedia.org/wiki/Mathematical_operators_and_symbols_in_Unicode#Letterlike_Symbols_block).
>
> Ex:
>
> >>> ℕ = [0, ...] # Whatever that means...
> >>> ℕ
> [0, Ellipsis]
>
> So yes, the language would need to be changed to allow the proper empty set unicode symbol to be used.
>
Not to mention everyone's keyboards. Python != APL. Err, I mean, Python ≠ APL.
ChrisA
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