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feat: BitVec.ushiftRight in terms of extractLsb' #6745

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merged 1 commit into from
Jan 22, 2025
Merged

feat: BitVec.ushiftRight in terms of extractLsb' #6745

merged 1 commit into from
Jan 22, 2025

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@bollu bollu commented Jan 22, 2025

This PR supports rewriting ushiftRight in terms of extractLsb'. This is the companion PR to #6743 which adds the similar lemmas about shiftLeft.

theorem ushiftRight_eq_zero {x : BitVec w} {n : Nat} (hn : w ≤ n) :
    x >>> n = 0#w

theorem ushiftRight_eq_extractLsb'_of_lt {x : BitVec w} {n : Nat} (hn : n < w) :
    x >>> n = ((0#n) ++ (x.extractLsb' n (w - n))).cast (by omega)

@bollu bollu requested a review from kim-em as a code owner January 22, 2025 18:24
@github-actions github-actions bot added the toolchain-available A toolchain is available for this PR, at leanprover/lean4-pr-releases:pr-release-NNNN label Jan 22, 2025
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Mathlib CI status (docs):

  • ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 6ebce421423445eeac59a6f4347a562897a99e8d --onto 9b74c07767dc50645efa00356a7724e7f7176227. (2025-01-22 18:44:27)

@hargoniX hargoniX added changelog-doc Documentation changelog-language Language features, tactics, and metaprograms and removed changelog-doc Documentation labels Jan 22, 2025
@hargoniX hargoniX added this pull request to the merge queue Jan 22, 2025
Merged via the queue into leanprover:master with commit 5f3c0da Jan 22, 2025
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luisacicolini pushed a commit to opencompl/lean4 that referenced this pull request Feb 24, 2025
@bollu @luisacicolini
feat: BitVec.ushiftRight in terms of extractLsb' (leanprover#6745)
307178f 
This PR supports rewriting `ushiftRight` in terms of `extractLsb'`. This
is the companion PR to leanprover#6743 which adds the similar lemmas about
`shiftLeft`.


```lean
theorem ushiftRight_eq_zero {x : BitVec w} {n : Nat} (hn : w ≤ n) :
    x >>> n = 0#w

theorem ushiftRight_eq_extractLsb'_of_lt {x : BitVec w} {n : Nat} (hn : n < w) :
    x >>> n = ((0#n) ++ (x.extractLsb' n (w - n))).cast (by omega)
```
luisacicolini pushed a commit to opencompl/lean4 that referenced this pull request Feb 25, 2025
@bollu @luisacicolini
feat: BitVec.ushiftRight in terms of extractLsb' (leanprover#6745)
7a79f56 
This PR supports rewriting `ushiftRight` in terms of `extractLsb'`. This
is the companion PR to leanprover#6743 which adds the similar lemmas about
`shiftLeft`.


```lean
theorem ushiftRight_eq_zero {x : BitVec w} {n : Nat} (hn : w ≤ n) :
    x >>> n = 0#w

theorem ushiftRight_eq_extractLsb'_of_lt {x : BitVec w} {n : Nat} (hn : n < w) :
    x >>> n = ((0#n) ++ (x.extractLsb' n (w - n))).cast (by omega)
```
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