Provides operations related to lists of forms.

`type 'a list_modifier````=` `{`

`transform : elt. 'elt list ‑> create_new_form:(?⁠init:'a ‑> unit ‑> 'elt) ‑> 'elt list;`

`}```
`val modify_list : State.t ‑> 'a List_id.t ‑> f:'a list_modifier ‑> State.t`

Modify list with a supplied `list_modifier` function.

Raises an exception if the resulting list contains duplicated instances of previously existing elements (although duplicating new elements is fine).

`val cons : State.t ‑> ?⁠init:'a ‑> 'a List_id.t ‑> State.t`

Add one empty form in front of the list

`val append : State.t ‑> ?⁠init:'a ‑> 'a List_id.t ‑> State.t`

Add one empty form to the end of the list.

`val remove_nth : State.t ‑> 'a List_id.t ‑> int ‑> State.t`

Remove n-th form from the list. If `int` is invalid index (i.e. `int` < 0 or `int` >= length of the list), the list remains unchanged and no exceptions are raised.