Definite or indefinite article for non-singletons?

[Terry Reedy]

On 7/27/2019 5:10 PM, Chris Angelico wrote:
> When talking about indistinguishable objects, is it correct to talk
> about "the <x>" or "an <x>"?
> 
> Example:
> 
> def f(s):
>      """Frob a thing.
> 
>      If s is an empty string, frobs all the things.
>      OR
>      If s is the empty string, frobs all the things.
>      """

Depends on whether one is using 'is' in the Python sense of object 
identify or the natural language sense of value equality.  To evade, 
avoid the (an?) article.

If string s is empty,...

I think we tend to be clearer about numbers.

x is an instance of 3.14.
x is a float equal to 3.14.
x is the number 3.14.
x is the float 3.14.

> It's entirely possible that a Python implementation will optimize
> small strings and thus have exactly one empty string, but it's also
> entirely possible to have multiple indistinguishable empty strings.
> Grammatically, is it better to think of empty strings as an entire
> category of object, and you were passed one from that category ("an
> empty string"), or to think of zero-length instances of 'str' as being
> implementation details referring to the one and only Platonic "empty
> string"?
> 
> Does it make a difference to usage if the object is mutable? For
> instance, would you say "the empty string" but "an empty set"?

In mathematics, *every* set is 'the'.

-- 
Terry Jan Reedy