[Python-3000] Immutable lists

[Nick Coghlan]

Greg Ewing wrote:
> Nick Coghlan wrote:
> 
>> This is exactly what I was trying to get at when I suggested using 
>> "tuple[T]" as the notation for an arbitrary length tuple with elements 
>> of type T
> 
> If tuple[T] is an arbitrary-length tuple, then how
> do you spell a 1-tuple with element type T?

(T,)

>  > and "T1, T2" as the notation for a 2-tuple with the first
>> element of type T1 and the second element of type T2.
> 
> It's been pointed out that making (T1, T2) equivalent to
> tuple[T1, T2] leads to an inconsistency. That needs to be
> resolved before taking this idea any further.

Yes - I'm saying tuple[T1, T2] should describe an arbitrary length tuple whose 
elements are 2-tuples, *instead* of being equivalent to (T1, T2).

Since we have 2 notations (a tuple of type descriptions, and a subscript 
operation on the tuple type) and 2 concepts to be expressed (a type 
description for a heterogeneous tuple and a type description for an arbitrary 
length tuple), it makes sense to me to use one of the notations for each 
concept rather than making the two notations mean the same thing.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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