[isabelle-dev] lists of n elements

[Tobias Nipkow]

On 04/08/2022 17:49, Peter Lammich wrote:
> In the AFP we have four separate copies of the definition
>>>
>>> definition list :: "nat \<Rightarrow> 'a set \<Rightarrow> 'a list set"
>>> where
>>>   "list n A = {xs. size xs = n \<and> set xs \<subseteq> A}"
>>>
> The naming of the lemmas suggests that this function should be named lists, not 
> list.

The motivation for "list" what is that in should mimic the name of the type 
constructor "list". On the level of types of rules omitted, e.g. nat not nats.

However I think these days I would also use the plural of the term level.

Tobias

> -- 
> 
>    Peter
> 
> 
>>> Interestingly, the exact same concept is coded in three different ways in the 
>>> four definitions. We also have a number of theorems in the repository 
>>> referring to this concept:
>>>
>>> finite_lists_length_eq
>>> set_n_lists
>>> card_lists_length_eq
>>> lists_length_Suc_eq
>>>
>>> And we have three copies of Listn.thy in MicroJava and JinjaThreads. Could 
>>> maybe some fragment of this, if not the whole thing, be moved into Library?
>>
>> Definitely, go ahead! (I obviously prefer the def you quoted above)
>>
>> Tobias
>>
>>> Larry
>>>
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>>
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