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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