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Inequality functionality for norm_num #1567

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thorimur opened this issue Jan 14, 2023 · 2 comments
Closed

Inequality functionality for norm_num #1567

thorimur opened this issue Jan 14, 2023 · 2 comments

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@thorimur
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This is an issue for tracking inequality functionality needed in norm_num, including ≤, <, and ≠.

For ≠, the following example should work:

example {α} [DivisionRing α] [CharZero α] : (-1:α) ≠ 2 := by norm_num
@thorimur thorimur mentioned this issue Jan 14, 2023
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@thorimur thorimur linked a pull request Jan 14, 2023 that will close this issue
[Merged by Bors] - feat: =, ≠, <, and ≤ functionality for norm_num #1568
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@hrmacbeth hrmacbeth removed a link to a pull request Jan 14, 2023
[Merged by Bors] - feat: =, ≠, <, and ≤ functionality for norm_num #1568
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@hrmacbeth
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hrmacbeth commented Jan 14, 2023 •
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Thanks for opening this issue @thorimur, indeed this is very important functionality. I removed the Github link between this issue and #1568 because if they're linked then Github will "close" this issue when #1568 is merged, whereas we want the issue to stay open until the ≤ and < functionality is also implemented.

Edit: What goes around, comes around. It looks like the new version of #1568 will indeed knock off the whole issue.

@hrmacbeth hrmacbeth linked a pull request Jan 19, 2023 that will close this issue
[Merged by Bors] - feat: =, ≠, <, and ≤ functionality for norm_num #1568
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bors bot pushed a commit that referenced this issue Jan 22, 2023
@thorimur @digama0
feat: =, ≠, <, and ≤ functionality for norm_num (#1568)
3fbdae4 
This PR gives `norm_num` basic inequality (and equality) functionality (towards #1567), including the following:
```
example {α} [DivisionRing α] [CharZero α] : (-1:α) ≠ 2 := by norm_num
```
We implement basic logical extensions to handle `=` and `≠` together, namely `¬`, `True`, and `False`. `≠` is not given an extension, as it is handled by `=` and `¬`.

For now we only can prove `≠` for numbers given a `CharZero α` instance.

- [x] depends on: #1578 

Co-authored-by: Mario Carneiro <di.gama@gmail.com>
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digama0 commented Jan 22, 2023

Fixed in #1568

@digama0 digama0 closed this as completed Jan 22, 2023
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[Merged by Bors] - feat: =, ≠, <, and ≤ functionality for norm_num leanprover-community/mathlib4
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@digama0 @hrmacbeth @thorimur