Recording typeclass ancestors #

The "old" structure command currently does not record the parent typeclasses. This file defines the ancestor attribute to remedy this. This information is notably used by to_additive to map structure fields and constructors of a multiplicative structure to its additive counterpart.

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meta def tactic.ancestor_attr :

user_attribute unit (list name)

The ancestor attributes is used to record the names of structures which appear in the extends clause of a structure or class declared with old_structure_cmd set to true.

As an example:

set_option old_structure_cmd true

structure base_one := (one : ℕ)

structure base_two (α : Type*) := (two : ℕ)

@[ancestor base_one base_two]
structure bar extends base_one, base_two α

The list of ancestors should be in the order they appear in the extends clause, and should contain only the names of the ancestor structures, without any arguments.

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meta def tactic.get_tagged_ancestors (cl : name) :

tactic (list name)

Returns the parents of a structure added via the ancestor attribute.

On failure, the empty list is returned.

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meta def tactic.get_ancestors (cl : name) :

tactic (list name)

Returns the parents of a structure added via the ancestor attribute, as well as subobjects.

On failure, the empty list is returned.

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meta def tactic.find_ancestors :

name → expr → tactic (list expr)

Returns the (transitive) ancestors of a structure added via the ancestor attribute (or reachable via subobjects).

On failure, the empty list is returned.