Definite or indefinite article for non-singletons?

[MRAB]

On 2019-07-28 13:30, Cameron Simpson wrote:
> On 28Jul2019 10:32, Peter Otten <__peter__ at web.de> wrote:
>>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.
>>>     """
>>
>>Slightly OT:
>>
>>While I would write "an empty string" but happily accept "the empty string"
>>I stumbled upon "all *the* things". Shouldn't it be "all things"?
>>
>>Real question as I'm not a native speaker.
> 
> The collection is "the things". "all" qualifies it, versus, say, "some
> of the things" or "the first of the things" etc.
> 
[snip]

It's strange that "all the things" (meaning "all of the things") is OK, 
but otherwise it's "one of the things", "some of the things", etc.

That's English for you!