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Re: Atoms, Identifiers, and Primaries

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Date Thu, 18 Apr 2013 11:56:50 +1000
Subject Re: Atoms, Identifiers, and Primaries
From Chris Angelico <rosuav@gmail.com>
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On Thu, Apr 18, 2013 at 9:40 AM, Mark Janssen <dreamingforward@gmail.com> wrote:
> On Tue, Apr 16, 2013 at 8:55 PM, rusi <rustompmody@gmail.com> wrote:
>> On Apr 17, 7:57 am, Bruce McGoveran <bruce.mcgove...@gmail.com> wrote:
>>> 3.  Section 5.3.1 offers this definition of an attributeref:
>>>     attributeref ::= primary "." identifier
>>>
>>
>> One general comment I will make is regarding your distress at what you
>> call 'circular'
>> Circular just means recursive and recursion is the bedrock for
>> language-design.
>
> Rercursion the "bedrock" of language-design.  I don't think so.  From
> what I know, a well-defined language ends at its symbols.  It makes no
> use of "infinities".

There's a difference between infinite and recursive, though. I was
defining a function (it converted from JSON to an internal format) and
wanted to explain that not all of JSON would reliably round-trip (ie
be able to be translated to the internal format and then back again).
To describe what _would_ round-trip correctly, I used this simple yet
technically illegal description:

typedef valid string|array(valid)|object(string:valid)

In other words, a string is valid, and a list/array of valid elements
is valid, and a dictionary/mapping/object with string keys and valid
elements is valid. It's a recursive definition, but it can't go
infinite (self-references aren't valid - though this isn't stated by
the typedef); however, it can go arbitrarily deep.

ChrisA

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Thread

Atoms, Identifiers, and Primaries Bruce McGoveran <bruce.mcgoveran@gmail.com> - 2013-04-16 19:57 -0700
  Re: Atoms, Identifiers, and Primaries rusi <rustompmody@gmail.com> - 2013-04-16 20:55 -0700
    Re: Atoms, Identifiers, and Primaries Mark Janssen <dreamingforward@gmail.com> - 2013-04-17 16:40 -0700
      Re: Atoms, Identifiers, and Primaries alex23 <wuwei23@gmail.com> - 2013-04-17 17:29 -0700
        Re: Atoms, Identifiers, and Primaries Mark Janssen <dreamingforward@gmail.com> - 2013-04-17 17:41 -0700
        Re: Atoms, Identifiers, and Primaries Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-04-18 02:04 +0100
      Re: Atoms, Identifiers, and Primaries rusi <rustompmody@gmail.com> - 2013-04-18 00:40 -0700
    Re: Atoms, Identifiers, and Primaries Ian Kelly <ian.g.kelly@gmail.com> - 2013-04-17 18:33 -0600
      Re: Atoms, Identifiers, and Primaries Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-18 02:14 +0000
        Re: Atoms, Identifiers, and Primaries Ian Kelly <ian.g.kelly@gmail.com> - 2013-04-17 21:12 -0600
    Re: Atoms, Identifiers, and Primaries Mark Janssen <dreamingforward@gmail.com> - 2013-04-17 18:04 -0700
    Re: Atoms, Identifiers, and Primaries Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-04-18 02:08 +0100
    Re: Atoms, Identifiers, and Primaries Chris Angelico <rosuav@gmail.com> - 2013-04-18 11:56 +1000
    Re: Atoms, Identifiers, and Primaries Ian Kelly <ian.g.kelly@gmail.com> - 2013-04-17 21:10 -0600
  Re: Atoms, Identifiers, and Primaries Ian Kelly <ian.g.kelly@gmail.com> - 2013-04-17 01:21 -0600
    Re: Atoms, Identifiers, and Primaries 88888 Dihedral <dihedral88888@googlemail.com> - 2013-04-17 21:29 -0700
    Re: Atoms, Identifiers, and Primaries 88888 Dihedral <dihedral88888@googlemail.com> - 2013-04-17 21:29 -0700
  Re: Atoms, Identifiers, and Primaries Dave Angel <davea@davea.name> - 2013-04-17 07:07 -0400
  Re: Atoms, Identifiers, and Primaries Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-17 11:43 +0000
  Re: Atoms, Identifiers, and Primaries Bruce McGoveran <bruce.mcgoveran@gmail.com> - 2013-04-17 10:15 -0700
    Re: Atoms, Identifiers, and Primaries Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-18 04:43 +1000
      Re: Atoms, Identifiers, and Primaries rusi <rustompmody@gmail.com> - 2013-04-18 10:04 -0700

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