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Re: Atoms, Identifiers, and Primaries

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Date Wed, 17 Apr 2013 07:07:45 -0400
From Dave Angel <davea@davea.name>
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Subject Re: Atoms, Identifiers, and Primaries
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On 04/16/2013 10:57 PM, Bruce McGoveran wrote:
> These are terms that appear in section 5 (Expressions) of the Python online documentation.  I'm having some trouble understanding what, precisely, these terms mean.  I'd appreciate the forum's thoughts on these questions:
>
>
> 3.  Section 5.3.1 offers this definition of an attributeref:
>      attributeref ::= primary "." identifier
>
> Now, I was at first a little concerned to see the non-terminal primary on the right hand side of the definition, since primary is defined to include attributeref in section 5.3 (so this struck me as circular).  Am I correct in thinking attributeref is defined this way to allow for situations in which the primary, whether an atom, attributeref (example:  an object on which a method is called that returns another object), subscription, slicing, or call, returns an object with property identifier?
>

It is circular.  Nothing wrong with that.  It means that not only can 
you use
     a.b

but also
     a.b.c

and
     a.b.c.d.e.f.g

without any explicit limit.  if a non-circular definition were to be 
attempted, you might need a few dozen rules, just to cover what someone 
*might* happen to use in an expression.  Of course normally, one doesn't 
go much beyond a.b.c in a single expression.


-- 
DaveA

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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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