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Re: [ddlm-group] Simon's elide proposal

Dear Colleagues,

   I do, at present, prefer 2.7 to 3.  That seems to be true
of most programmers, but at some point we all will
face the question of making a transition to 3.  2.7 is
not restricted to ASCII characters.  3 is not restricted
to ASCII characters.  The main point here is that, because
3 has a default encoding of UTF-8, it always allows
the restriction to be relaxed, while 2.7, when you don't
specify an encoding for the file, defaults to a pure
ASCII encoding, and therefore does not allow you to
go beyond the ASCII character set.  In the earlier
decisions we adopted the approach of defaulting to
UTF-8 so the restriction would be relaxed.  However,
for the reasons discussed earlier, I think we need
to revisit _all_ the ealier decisions, so I am willing
to consider making the default encoding for a CIF2
be pure ASCII, if that is what John B. is proposing.

The reason the U and u prefixes are dropped in 3
is precisely because the  \u and \U escapes are
allowed in all string literals inasmuch as the
encoding is UTF-8, and the b prefix was dropped
a long time ago, leaving only the r""" and """
versions that Ralf proposed.

On the question of the mutability of the Python spec,
I agree, it is very, very mutable.  I know because I
have to teach it to students, and we get burned
all the time by the differences among 2.4, 2.6, 2.7
and 3.  I am not thrilled about that, so, yes,
we need to pick one of them (I prefer 2.7), but,
in the spirit of revisting all earier decisions,
I would certainly also be willing to consider other
possibilities.  However, I would hope that whatever
is proposed is clean, reasonably stable, well
supported code, with source and examples available,
much as both Python 2.7 and Python 3 are.

The real problem is that the entire computing world
is in a major transition, hopefully towards better
agreement on something sensible in handling strings
of characters.  Python seems to be in a reasonable
position with respect to the leading edge of that
transition, and I suggest we carefully review and
consider what they are doing, and make use, where
appropriate, of their efforts.  I think we will
need to try to track somebody, and Python looks
like a possibility.



=====================================================
  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769

                  +1-631-244-3035
                  yaya@dowling.edu
=====================================================

On Thu, 13 Jan 2011, Bollinger, John C wrote:

> On Thursday, January 13, 2011 12:42 PM, Herbert J. Bernstein wrote:
> [I wrote:]
>>> It should also be noted that Python source code, including its string
>>> literals, is restricted to being expressed in the characters of the
>>> 7-bit ASCII character set (though they need not necessarily be encoded
>>> according to US-ASCII).  Unconditional, bidirectional CIF/Python string
>>> compatibility would require that we apply the same restriction to CIF2
>>> triple-quoted strings.  I would oppose that.
>>
>> That started to change in Python 2.5 which allowed explicit encoding
>> declarations, and by Python 3 has vanished even without an
>> encoding declaration.  The Python 3 spec is:
>>
>> "Python reads program text as Unicode code points; the encoding
>> ... defaults to UTF8"
>
> Well and good, then.  You previously pointed us to Python 2.7.1 for 
> documentation of the Python semantics proposed for CIF, but Python 3 
> looks like a better fit.  Python 3 no longer provides the [uU] string 
> prefix, however, so that's different from what Ralf proposed and from 
> what I thought we had been discussing.  That begs the question, *which 
> version of Python* is proposed to provide its string syntax to CIF?
>
> This furthermore demonstrates one of the strategic drawbacks of adopting 
> Python semantics: Python is not static.  We could make CIF semantics 
> well defined by tying them to a specific Python version, perhaps v3.1.3, 
> but does that retain its purported advantages as Python semantics evolve 
> in 3.2, 3.5, 4.0, etc.?  Perhaps it does, but that's not obvious to me.
>
>
> John
>
> --
> John C. Bollinger, Ph.D.
> Department of Structural Biology
> St. Jude Children's Research Hospital
>
>
>
>
> Email Disclaimer:  www.stjude.org/emaildisclaimer
>
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