[Python-ideas] [Python-Dev] Unicode minus sign in numeric conversions

[M.-A. Lemburg]

On 09.06.2013 08:21, Terry Jan Reedy wrote:
> On 6/9/2013 1:30 AM, Guido van Rossum wrote:
>> I'm beginning to feel that it was even a mistake to accept all those
>> other Unicode decimal digits, because it leads to the mistaken belief
>> that one can parse a number without knowing the locale. Python's
>> position about this is very different from what the heuristics you
>> quote seem to suggest: "refuse the temptation to guess" leads to our
>> current, simple rule which only accepts '.' as the decimal indicator,
>> and leaves localized parsing strictly to the application (or to some
>> other library module).
> 
> The referenced algorithm is about extracting number literals, especially integel, out of text. Doing
> that 'properly' depends on local and purpose. Int is about converting a literal to its numberic
> value, whether written directly or extracted. Once a decision is made to convert a literal,
> conversion itself (for integers) is not location dependent.
> 
>> Still, I suppose I could defend the current behavior from the
>> perspective of writing such a localized parser -- at some point you've
>> got a digit and you need to know its numeric value, and it is
>> convenient that int(c) does so.
> 
> Exactly. I believe that is why it was extended to do that.

I added this support as part of the Unicode integration in Python 1.6
in order to support the full range of Unicode digits - just like
we support more characters and mappings for e.g. line breaks,
lower/upper case, etc. in Unicode than in 8-bit character sets.

Note that the decimal encoder does not support right-to-left scripts.

-- 
Marc-Andre Lemburg
eGenix.com

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