bbv makes it impossible to use $ as a prefix printing notation without parentheses

[JasonGross]

Word.v defines "$ x" to be a notation at level 0 (and similarly with #). This conflicts with the notations I want to use in fiat-crypto. Please put these notations in a Module (e.g., WordNotations) and do not export this module by default from any file.

[vmurali]

I ran into a similar issue. So I second this change. I also had an issue where $ not displaying the word size in natToWord was causing considerable anguish. As Jason suggested, it's best to put these notations in another module.

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On Sun, May 6, 2018, 20:17 Jason Gross ***@***.***> wrote: Word.v defines "$ x" to be a notation at level 0 (and similarly with #). This conflicts with the notations I want to use in fiat-crypto. Please put these notations in a Module (e.g., WordNotations) and do not export this module by default from any file. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#5>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAOaRWNFNaK1TalJ_b5q5Q6A4PQDivloks5tv7zkgaJpZM4T0WF8> .

[andres-erbsen]

Is there actually a good reason why $ should be at the extreme level of 0, as opposed to something like 10 (same as function application)? Since both of these are breaking changes, it may make sense to do them together.

[samuelgruetter]

Also, some notations are in word_scope, while others don't have an explicit scope, is there any reason for this other than historical?
Not opening word_scope provides some protection from unwanted notations, but probably not what @JasonGross needs, because even if you don't open word_scope, the notations still define the level and associativity in an irreversible way, so they should really be in a separate module.

[samuelgruetter]

@andres-erbsen if you put $ at level 10, you have to write f ($4) ($5) instead of f $4 $5, which I think is undesirable. Level 9 is the highest level where f $4 $5 still works. Do you have a particular other notation in mind which would benefit from changing the level of $?

[andres-erbsen]

f $4 $5 sounds like an use case that I don't want to argue against, so feel free to pick any level below 10 or keep it at 0 as you wish. Overall, I think avoiding bringing in notations is a better approach than trying to make them compatible -- after all, Haskell people would probably want to put $ at level 100 or something like that to act as ( ... ) $ ( ... )...

[JasonGross]

I would like to put it at level 9, x at level 10 for usage in fiat-crypto, so that it displays without the parentheses, which is incompatible both with at level 9 and with at level 10 (and with at level 0). This is why I want it to not be exported by default anywhere.

[samuelgruetter]

What exactly do you mean by "displays without parentheses"? I can do the following, is this what you meant?

Definition word(sz: nat): Set. Admitted.
Definition natToWord (sz n : nat) : word sz. Admitted.


Notation "$ n" := (natToWord _ n) (at level 0, n at level 0, format "$ n") .

Definition f{sz}(a b c: word sz): word sz. Admitted.

Definition a: nat := 7.
Definition t: word 8 := f $a $5 $(3 + 4).

Print t. (* prints "f $a $5 $(3 + 4)" *)

Whereas currently, this would print as f $ (a) $ (5) $ (3 + 4). I think it would be nice to have $ without parentheses in Word.v too.

[JasonGross]

Yes, that is what I meant. But, even with this change, I think that both # and $ should be in their own module and not exported by default.

[vmurali]

If you really want these notations inside Word.v also, you can define a Local Notation inside Word.v in addition to the separate module exporting these notations globally. As I have said earlier, hiding the size parameter in [natToWord] makes it difficult to do bit-manipulation proofs. The workaround is clunky, requiring another notation to mask the default notation. Instead, it's better to have the flexibility to choose whether or not we want these notations orthogonal to whether or not we want to use the definitions and theorems in Word.v.

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On Tue, May 8, 2018 at 12:25 PM, Jason Gross ***@***.***> wrote: Yes, that is what I meant. But, even with this change, I think that both # and $ should be in their own module and not exported by default. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#5 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAOaRbUMEKFZIUyVMVKYJ8dVrcjd0n1Sks5twfEcgaJpZM4T0WF8> .

[samuelgruetter]

Yes of course we should put the notations inside a module, I was just wondering whether we can get parenthesis-less $ in bbv too because I think that would be nice.

Moreover, it would also be nice if the lemmas in Word.v could still use $, to avoid big refactoring effort. Do you think it would be ok to have the following code inside Word.v? (As in, is $ isolated enough to not spoil what you or anyone else in the future wants to do?)

Module WordNotations.

Notation "$ n" := (natToWord _ n) (at level 0, n at level 0, format "$ n") .

(* more notations... *)

End WordNotations.

Import WordNotations. (* but not exported *)

(* lemmas happily using $ ... *)

[vmurali]

I am fine with this. I believe it is similar to the notations in List.v.

[samuelgruetter]

@JasonGross would you mind submitting a PR for this?

[vmurali]

Bump. Can we get this done? I don't mind submitting a pull request for this.

[samuelgruetter]

Yes, please submit a PR @vmurali!
I just merged #9, so you can have the "edit lock" for some time 😉

[JasonGross]

Note also that putting # at level 0 breaks the infix # notation from the QArith stdlib module.