Are the critiques in "All the things I hate about Python" valid?

[Richard Damon]

On 2/18/18 8:16 PM, Ben Finney wrote:
> Dennis Lee Bieber <wlfraed at ix.netcom.com> writes:
>
>> On Mon, 19 Feb 2018 00:09:40 +0000 (UTC), Steven D'Aprano
>> <steve+comp.lang.python at pearwood.info> declaimed the following:
>>
>>> Or more realistically, suppose you want your type system to ensure
>>> that you don't lay off the wrong workers:
>>>
>>> "employee records where the length of employment is greater than six
>>> months but less than five years, AND the salary is greater than
>>> $100,000 or less than $40,000, AND the average number of paid sick
>>> days taken per year over the last three years is less than five, AND
>>> the number of reprimands is zero in the last year and less than two
>>> in the last five years, AND the position in the last two stack
>>> rankings was in the top fifty percent"
>>>
>> 	That's not a data type -- that's an SQL query...
> If that isn't part of the definition of the data type, then *the type
> checker is not going to help* to determine whether the code lays off the
> wrong workers.
Doesn't sound like the sort of thing that you should expect a Type 
Checker to find.

Now, perhaps you could define a type of something like 
'Layoffable_Employee' with an invariant based on the above, then the 
layoff module could insist that it will only that an 
Layoffable_Employee, and the type uses pre-/post- conditions to confirm 
the needed conditions.

Now, somewhere in the code you probably started with an Employee, and 
then to pass it to the module you will need to convert the type of the 
object (it seems unlikely that such a type is inherent in most of the 
rest of the code). This is why it doesn't make sense for it to be a 
'Type', but more likely an attribute/predicate of the object, that the 
Layoff module can confirm as a pre-condition.
>
>> 	The data type is still "employee"
> I think you're agreeing with Steven. Static data types are not relevant
> for finding most of the bugs a program can have.
>

-- 
Richard Damon