Re: [ddlm-group] Use of elides in strings

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From: Nick Spadaccini <nick@csse.uwa.edu.au>
To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
Sent: Monday, 23 November, 2009 8:13:20
Subject: Re: [ddlm-group] Use of elides in strings

I now see why we have confused things for Herb. Implicit in our proposal is
that a terminator character is elided ONLY when there is ambiguity because
the same character is used as the string delimiters.

We could make it that both the " and ' characters HAVE to be elided when
ever they appear in ", ' or """ delimited strings, but I favour the case
that they are elided only when they have to. James examples are predicated
on that interpretation.

I add my comments below his with the assumption we are adopting the eliding
of " only when in " or """ strings, and the eliding of ' only when in ' or
''' strings.


On 23/11/09 1:20 PM, "James Hester" <jamesrhester@gmail.com> wrote:

> For what it is worth, I have inserted my understanding of what NIck
> and I propose as a minimal eliding system, by referring to Nick's
> previous emails in this thread.
>
> The asterisks indicate transformations that we haven't discussed here,
> as in these cases we have terminator sequences rather than single
> characters.  Other approaches are possible in these cases, as the
> terminator sequence can be broken up.  In these cases custom
> dictionary-driven eliding is probably much more reasonable, ie. the
> syntax specification would not provide an eliding mechanism and the
> cut-and-paste brigade might get a bit more mileage.
>
> On Mon, Nov 23, 2009 at 3:13 PM, Herbert J. Bernstein
> <yaya@bernstein-plus-sons.com> wrote:
>> I am now totally lost.  Please start over with a coherent proposal
>> for the syntax of a quoted string.  In particular, please state
>> how the following strings will be parsed
>>
>> "ab\"cd"                -> ab"cd
>> 'ab\"cd'                      ab\"cd
>> "ab\\"cd"                    ab\"cd
>> 'ab\\"cd'                    ab\\"cd

Agreed to all of the above.

>> ;ab\"cd\                    (*)
>> ;

I see no ambiguity here so I would say
ab\"cd\\n
(the \n being the single byte newline and assuming there aren't trailing
spaces on the first line)

>>
>> ;ab\\"cd\\                  (*)
>> ;

I see no ambiguity here so I would say
ab\\"cd\\\n
(the \n being the single byte newline and assuming there aren't trailing
spaces on the first line)

NOT WITHSTANDING IN BOTH CASES that the elide before the newline may
actually mean a wrap around - but that is defined at a dictionary level.

>> """ab\""""                  (*)

I have argued previously this is
ab"

>> """ab\\""""                  (*)

This would be

ab\"

>> {"abcd\"":ggg}          {abcd":ggg}
>> {'abcd\"':ggg}          {abcd\":ggg}

Agreed.

>> "resum\'ee"              resum\'e
>> 'resum\'ee'              resum'e

Agreed.

I believe given our proposal, this is a consistent interpretation. It is
easy to implement and will cover all classes of " and ' embedding.

cheers

Nick

--------------------------------
Associate Professor N. Spadaccini, PhD
School of Computer Science & Software Engineering

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