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Continuity of linear functions in finite dimension

Motivation for this change
Checklist
  • added corresponding entries in CHANGELOG_UNRELEASED.md
  • added corresponding documentation in the headers

Reference: How to document

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    all compile are preferentially merged into master.
  • PRs with disorganized commits are very likely to be squash-rebased.
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@CohenCyril
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@mkerjean FYI

Let V' := @fullv _ V.
Hypothesis (Bbasis : basis_of V' B).

Definition oo_norm x := \big[Order.max/0]_(i < \dim V') `|coord B i x|.
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Is it really a good name? Because it is a bit like using a notation inside an identifier, also we have been using oo to mean "open-open" in MathComp (when talking about intervals). What about infty_norm? (like in LaTeX). Possibly coupling it with a notation using +oo in some way.

@affeldt-aist affeldt-aist self-requested a review September 24, 2025 09:04
Comment on lines +2204 to +2208
Lemma equivalence_norms (N : V -> R) :
N 0 = 0 -> (forall x, 0 <= N x) -> (forall x, N x = 0 -> x = 0) ->
(forall x y, N (x + y) <= N x + N y) ->
(forall r x, N (r *: x) = `|r| * N x) ->
exists M, 0 < M /\ forall x : Voo, `|x| <= M * N x /\ N x <= M * `|x|.
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@CohenCyril CohenCyril Oct 16, 2025

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I think this deserve an abstraction of norm and an abstraction of norm comparison :)

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3 participants