Instances for dependent function types #1383

Tragicus · 2024-11-05T15:46:02Z

Motivation for this change

Generalizes the instances on function types to dependent function types. The same generalization is happening in mathcomp (see math-comp/math-comp#1256) and it needs to be done here first for backwards compatibility.
EDIT: WIP because we are waiting for unification features in Coq that make unifying dependent functions work.

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added corresponding entries in CHANGELOG_UNRELEASED.md

added corresponding documentation in the headers

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affeldt-aist · 2024-11-06T13:53:59Z

altreals/realseq.v

 move=> cu cv; pose a := u \- lu%:S; pose b := v \- lv%:S.
 have eq: (u \* v) =1 (lu * lv)%:S \+ ((lu%:S \* b) \+ (a \* v)).
-  move=> n; rewrite {}/a {}/b /= [u n+_]addrC [(_+_)*(v n)]mulrDl.
+move=> n; rewrite {}/a {}/b /= [u n+_]addrC [(_+_)*(v n)]mulrDl.


Suggested change

move=> n; rewrite {}/a {}/b /= [u n+_]addrC [(_+_)*(v n)]mulrDl.

move=> n; rewrite {}/a {}/b /= [u n+_]addrC [(_+_)*(v n)]mulrDl.

affeldt-aist · 2024-11-06T13:55:28Z

classical/functions.v

-Next Obligation. by move=> T M f g h; rewrite funeqE=> x/=; rewrite mulrDr. Qed.
 Next Obligation.
-by move=> T M ; apply/eqP; rewrite funeqE => /(_ point) /eqP; rewrite oner_eq0.
+by move=> T M f g h; apply/functional_extensionality_dep => x /=; rewrite addrA.


We have funext for non-dependent functional extensionality.
Maybe we should introduce funext_dep for uniformity and to save some typing.

affeldt-aist · 2024-11-06T13:56:00Z

classical/functions.v

+Proof.
+by apply/funext => x/=; rewrite mulrC. Qed.


Suggested change

Proof.

by apply/funext => x/=; rewrite mulrC. Qed.

Proof. by apply/funext => x/=; rewrite mulrC. Qed.

affeldt-aist · 2024-11-06T13:57:06Z

theories/derive.v

 move=> df; apply/eqaddoP => _/posnumP[e].
 rewrite -nbhs_nearE nbhs_simpl /= dnbhsE; split; last first.
-  rewrite /at_point opprD -![(_ + _ : _ -> _) _]/(_ + _) scale0r add0r.
+  rewrite /at_point opprD !add_funE !opp_funE/= scale0r add0r.


This looks indeed a bit better ^_^.

affeldt-aist · 2024-11-06T14:00:05Z

theories/derive.v

 Proof.
-move=> dfc dxf; apply/subr0_eq; rewrite -[LHS]/(_ \- _).
-apply/littleo_linear0/eqoP/eq_some_oP => /=; rewrite funeqE => y /=.
+move=> dfc dxf; apply/subr0_eq/(littleo_linear0 (f:=GRing.sub_fun _ _))/eqoP.


It is desirable to avoid using (f:= ...) because it relies on the naming of a variable that is likely to change. (There are instances of this issue below with df:=.)

affeldt-aist · 2024-11-06T14:01:02Z

theories/derive.v

 Proof.
-by elim/big_ind : _ => // ? ? g h ?; apply: differentiableD; [exact:g|exact:h].
+elim/big_ind : _ => //[_|? ? g h ?]; first exact/(@differentiable_cst _ 0).
+apply: differentiableD; [exact:g|exact:h].


Suggested change

apply: differentiableD; [exact:g|exact:h].

by apply: differentiableD; [exact:g|exact:h].

affeldt-aist · 2024-11-06T14:02:06Z

theories/ftc.v

 have DPGFE : {in `]a, b[, (- (PG \o F))%R^`() =1 ((G \o F) * (- f))%R}.
-  move=> x /[dup]xab /andP[ax xb]; rewrite derive1_comp //; last first.
+  move=> x /[dup]xab /andP[ax xb].
+  rewrite (derive1_comp (g:[email protected] R)) //; last first.


Maybe avoid the (g:= ...) syntax if possible.

affeldt-aist · 2024-11-06T14:04:22Z

theories/lebesgue_measure.v

  measurable_fun D g -> measurable_fun D (f \- g).
-Proof. by move=> ? ?; apply: measurable_funD =>//; exact: measurableT_comp. Qed.
+Proof.
+move=> ? ?; apply: measurable_funD =>//; exact: measurableT_comp.


Suggested change

move=> ? ?; apply: measurable_funD =>//; exact: measurableT_comp.

by move=> ? ?; apply: measurable_funD =>//; exact: measurableT_comp.

affeldt-aist · 2024-11-06T14:15:09Z

theories/lebesgue_integral.v

 Proof.
 split=> [|f g|f g]; rewrite !inE/=.
- exact: measurable_cst.
+- exact: measurable_cst (1 : rT).


Mmmhhh... There are now plenty of lemma applications with blah_cst lemmas that now require an explicit mention of the constant in question. This looks problematic.

affeldt-aist · 2024-11-06T14:21:29Z

theories/derive.v

-Proof. by case: n => [_|n /derivableP]; [rewrite expr0|]. Qed.
+Proof.
+case: n => [_|n /derivableP]; last by [].
+by rewrite expr0; apply/(derivable_cst (1 : R)).


Indeed, if I remove the (1 : R) type checking does not seem to terminate. Do you know why?

affeldt-aist

What is the justification for the mandatory addition of constants for the application of blah_cst lemmas? Do we know where the problem comes from?

affeldt-aist · 2024-11-06T14:40:15Z

I observe that this PS shares similarities with PR #1379 while the latter is marked as draft. Maybe you intended this one as well to be a draft?

Tragicus · 2024-11-06T15:47:54Z

What is the justification for the mandatory addition of constants for the application of blah_cst lemmas? Do we know where the problem comes from?

cst is not dependent (and can not be), so I can not define the operations on dependent functions using it. Then, when Rocq tries to unify cst ?c with 1 : U -> V, it reduces the problem to fun=> ?c = fun t : U => GRing.one ((fun=> V) t) and then to ?c = GRing.one ((fun=> V) t). This fails because ?c can not use t in its instantiation. I believe I have a solution for that, but it needs to be integrated into Coq, so it will take some time, and the impact looks minor according to the CI.

Tragicus · 2024-11-06T15:49:48Z

I extracted this from the other PR and extended it when I realized I needed to generalize things here first. It is ready for review.

affeldt-aist reviewed Nov 6, 2024

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affeldt-aist self-requested a review November 6, 2024 14:21

affeldt-aist requested changes Nov 6, 2024

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affeldt-aist mentioned this pull request Nov 6, 2024

Structures with one operation math-comp/math-comp#1256

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instances for dependent function types

b6c10bc

Tragicus force-pushed the dep-inst branch from 38a49d4 to b6c10bc Compare November 6, 2024 16:44

Tragicus changed the title ~~Instances for dependent function types~~ [WIP] Instances for dependent function types Feb 19, 2025

affeldt-aist marked this pull request as draft September 24, 2025 09:09

affeldt-aist changed the title ~~[WIP] Instances for dependent function types~~ Instances for dependent function types Sep 24, 2025

	move=> n; rewrite {}/a {}/b /= [u n+_]addrC [(_+_)*(v n)]mulrDl.
	move=> n; rewrite {}/a {}/b /= [u n+_]addrC [(_+_)*(v n)]mulrDl.

	Proof.
	by apply/funext => x/=; rewrite mulrC. Qed.
	Proof. by apply/funext => x/=; rewrite mulrC. Qed.

	apply: differentiableD; [exact:g\|exact:h].
	by apply: differentiableD; [exact:g\|exact:h].

	move=> ? ?; apply: measurable_funD =>//; exact: measurableT_comp.
	by move=> ? ?; apply: measurable_funD =>//; exact: measurableT_comp.

Instances for dependent function types #1383

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affeldt-aist commented Nov 6, 2024

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Tragicus commented Nov 6, 2024

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