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[ fix #1443 ] Fin & Vec casts and properties #1839

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Merged
merged 4 commits into from
Oct 4, 2022

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gallais
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@gallais gallais commented Sep 30, 2022

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@jamesmckinna
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Just one query about the type

cast-is-subst : cast eq k ≡ subst Fin eq k

The name of this term (going from left-to-right) is consistent with the other cast-is-* terms.

But to me, the type seems the wrong way round?

If the general aim of equations in the std-lib is to 'reduce complex expressions to simpler', then in this instance, and for all the reasons previously discussed for preferring cast to subst, then shouldn't this equation be oriented from subst in favour of cast?, ie

subst-is-cast : subst Fin eq k ≡ cast eq k

If not, I'd love to be have that spelt out.

Either way, I'm otherwise happy with this PR as it stands.

@JacquesCarette
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I agree with @jamesmckinna on the 'wanted' direction of that one lemma, and on this otherwise being ready.

@MatthewDaggitt MatthewDaggitt linked an issue Oct 4, 2022 that may be closed by this pull request
@MatthewDaggitt MatthewDaggitt merged commit a123840 into agda:master Oct 4, 2022
jamesmckinna added a commit to jamesmckinna/agda-stdlib that referenced this pull request Oct 4, 2022
@gallais gallais deleted the fin-cast branch October 4, 2022 14:44
@andreasabel andreasabel mentioned this pull request Aug 27, 2023
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Missing cast properties
4 participants