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

[Chris Angelico]

On Thu, Jul 21, 2016 at 4:26 PM, Rustom Mody <rustompmody 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?

This debate should probably continue on python-list (if anywhere). I
doubt Python is going to change its normalization rules any time soon,
and if it does, it'll need a very solid reason (and probably a PEP
with all the pros and cons).

ChrisA