Partially applied constant on left hand side of code equation

问题

I need to use nat_plus_commute.fold_set_fold_remdups code equation instead of Finite_Set.fold_def:

interpretation nat_plus_commute: comp_fun_commute "plus :: nat ⇒ nat ⇒ nat"
  by standard auto

declare Finite_Set.fold_def [code del]
declare nat_plus_commute.fold_set_fold_remdups [code]

The problem is that the first equation is defined only for plus operation and so I get the following warning:

Partially applied constant "Groups.plus_class.plus" on left hand side of equation, in theorem:
Finite_Set.fold op + ?y (set ?xs) ≡ fold op + (remdups ?xs) ?y

As result the following statement

value "Finite_Set.fold plus 0 (set [1::nat, 2])"

returns the exception:

exception Fail raised (line 29 of "generated code"): Finite_Set.fold

Is it possible to use a specialized code equation for specific operations (plus) and types (nat)?

回答1:

I am not quite sure want you want to achieve, but note that Finite_Set.fold is a low-level construct of which other operations with practically usable properties can only be derived with considerable effort, cf. theories src/HOL/Finite_Set.thy and src/HOL/Groups_Big.thy for a rough idea.

For summation on finite sets and lists, there are sum and sum_list which are already equipped with code equations.

来源：https://stackoverflow.com/questions/46784091/partially-applied-constant-on-left-hand-side-of-code-equation