# Re: [isabelle] bundle commands inside a locale

Dear Anonymous,
I am far from being an expert on notation/bundles. Therefore, hopefully,
someone else will provide a better reply. However, given your examples, I
do not understand why would it not be suitable to merely provide the
notation explicitly inside the locale Foo using the command notation?
For example,
locale Foo =
fixes A :: "'a => bool"
assumes "P A"
begin
definition t :: "'a ⇒ bool" ("TTT _" [50]) where "t == A"
notation t ("TTT _" [50])
lemma "TTT x ⟹ A x" unfolding t_def .
end
locale Bar =
fixes B :: "'a ⇒ bool"
assumes a1:"P B" and "Q B"
begin
interpretation Foo B using a1 .
lemma "TTT x ⟹ B x" by (simp add: t_def) (*the notation is now available*)
end
Alternatively, in my own work, usually, for each locale, I provide another
locale with the notation specified explicitly (I adopted this method from
an answer to one of my own old and rather naive questions that was provided
by Akihisa Yamada:
https://stackoverflow.com/questions/50085849/importing-classes-into-a-locale-in-isabelle-and-other-related-questions).
This allows me to switch between different notations if necessary. However,
this method does incur a certain amount of boilerplate code. Quite frankly,
I would also be interested to know if there is a more standard approach
that would allow for switching between different sets of notation with
ease.
Thank you
--
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