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Lies in education [was Re: The "loop and a half"]

bartc bc at freeuk.com
Fri Oct 13 11:15:35 EDT 2017 
On 13/10/2017 15:59, Julien Salort wrote:
> Le 12/10/2017 à 17:57, bartc a écrit :
> 
>> With a const struct, you are stopped from directly modifying elements, 
>> but if an element is a pointer, nothing stops you writing to what the 
>> pointer points to, unless that has a const target too. And then you've 
>> going to have problems doing normal updates. This constness just 
>> insinuates itself everywhere.
> 
> That is not very different from the mutable/immutable concept in Python, 
> is it ?
> A tuple is immutable, but if it contains a mutable object, nothing 
> prevents you from mutating it.
> Does it mean you think the mutable/immutable concept of Python is flawed?

When you put it like that, then yes!

But it depends on how you define the value of a tuple. If that is a 
recursive definition that includes all nested object levels, then it 
would be harder to keep the whole thing constant.

If you look only one level deep, then it can be fully immutable (never 
mind that some elements could be functions that will give a different 
result each time they are evaluated).


-- 
bartc
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