[Python-ideas] allow `lambda' to be spelled λ

[Chris Angelico]

On Thu, Jul 21, 2016 at 5:47 PM, Rustom Mody <rustompmody at gmail.com> wrote:
>> On Thu, Jul 21, 2016 at 4:26 PM, Rustom Mody <rusto... at gmail.com> wrote:
>> > IOW
>> > 1. Disallow co-existence of confusables (in identifiers)
>> > 2. Identify confusables to a normal form — like case-insensitive
>> > comparison
>> > and like NKFC
>> > 3. Leave the confusables to confuse
>> >
>> > My choice
>> > 1 better than 2 better than 3
>>
>> So should we disable the lowercase 'l', the uppercase 'I', and the
>> digit '1', because they can be confused? What about the confusability
>> of "m" and "rn"? O and 0 are similar in some fonts. And case
>> insensitivity brings its own problems - is "ss" equivalent to "ß", and
>> is "ẞ" equivalent to either? Turkish distinguishes between "i", which
>> upper-cases to "İ", and "ı", which upper-cases to "I".
>>
>> We already have interminable debates about letter similarities across
>> scripts. I'm sure everyone agrees that Cyrillic "и" is not the same
>> letter as Latin "i", but we have "AАΑ" in three different scripts.
>> Should they be considered equivalent? I think not, because in any
>> non-trivial context, you'll know whether the program's been written in
>> Greek, a Slavic language, or something using the Latin script. But
>> maybe you disagree. Okay; are "BВΒ" all to be considered equivalent
>> too?  What about "СC"? "XХΧᚷ"? They're visually similar, but they're
>> not equivalent in any other way. And if you're going to say things
>> should be considered equivalent solely on the basis of visuals, you
>> get into a minefield - should U+200B ZERO WIDTH SPACE be completely
>> ignored, allowing "AB" to be equivalent to "A\u200bB" as an
>> identifier?
>>
>>
>
> I said 1 better than 2 better than  3
> Maybe you also want to add:
>
> Special cases aren't special enough to break the rules.
> Although practicality beats purity.
>
> followed by
>
> Errors should never pass silently.
>
> IOW setting out 1 better than 2 better than 3 does not necessarily imply its
> completely achievable

No; I'm not saying that. I'm completely disagreeing with #1's value. I
don't think the language interpreter should concern itself with
visually-confusing identifiers. Unicode normalization is about
*equivalent characters*, not confusability, and I think that's as far
as Python should go.

ChrisA