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PEP 622: Don't use "ADT" for "algebraic data types" 

ADT already means Abstract Data Types (a different concept).
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Guido van Rossum 2020-06-24 18:14:29 -07:00
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@ -781,14 +781,14 @@ every class is matchable and therefore is subject to the checks specified
above. above.
Sealed classes as ADTs Sealed classes as algebraic data types
---------------------- --------------------------------------
Quite often it is desirable to apply exhaustiveness to a set of classes without Quite often it is desirable to apply exhaustiveness to a set of classes without
defining ad-hoc union types, which is itself fragile if a class is missing in defining ad-hoc union types, which is itself fragile if a class is missing in
the union definition. A design pattern where a group of record-like classes is the union definition. A design pattern where a group of record-like classes is
combined into a union is popular in other languages that support pattern combined into a union is popular in other languages that support pattern
matching and is known under a name of algebraic data types [2]_ or ADTs. matching and is known under a name of algebraic data types [2]_.
We propose to add a special decorator class ``@sealed`` to the ``typing`` We propose to add a special decorator class ``@sealed`` to the ``typing``
module [6]_, that will have no effect at runtime, but will indicate to static module [6]_, that will have no effect at runtime, but will indicate to static
@ -797,8 +797,8 @@ be defined in the same module as the base class.
The idea is that since all subclasses are known, the type checker can treat The idea is that since all subclasses are known, the type checker can treat
the sealed base class as a union of all its subclasses. Together with the sealed base class as a union of all its subclasses. Together with
dataclasses this allows a clean and safe support of ADTs in Python. Consider dataclasses this allows a clean and safe support of algebraic data types
this example:: in Python. Consider this example::
from dataclasses import dataclass from dataclasses import dataclass
from typing import sealed from typing import sealed