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feat(GRewrite): support strict rewriting in >/≥ #41503

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feat(GRewrite): support strict rewriting in >/≥ #41503

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feat(GRewrite): also support strict rewriting in `≥`/`>`
JovanGerb Jul 8, 2026
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JovanGerb Jul 8, 2026
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3 changes: 3 additions & 0 deletions Mathlib/Order/Basic.lean
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Expand Up @@ -191,6 +191,9 @@ theorem gt_imp_gt_of_le_of_le (h₁ : a ≤ c) (h₂ : d ≤ b) : a > b → c >

attribute [gcongr strict] lt_of_lt_of_le lt_of_lt_of_le'

@[to_dual (attr := gcongr strict) ge_imp_gt_of_lt']
theorem ge_imp_gt_of_lt (h : a < b) : a ≥ c → b > c := lt_of_lt_of_le' h

namespace Mathlib.Tactic.GCongr
open Lean Meta

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6 changes: 6 additions & 0 deletions MathlibTest/Tactic/GRewrite.lean
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Expand Up @@ -477,6 +477,12 @@ example (h₁ : a ≤ b) (h₂ : b < c) : a < c := by
example (h₁ : a ≤ b) (h₂ : b < c) : a < c := by
by_contra!; grw [← h₂, ← h₁] at this; contrapose! this; rfl

example (h₁ : a < b) (h₂ : b ≤ c) : c > a := by
grw [h₁, h₂]

example (h₁ : a < b) (h₂ : b ≤ c) : c > a := by
grw [← h₂, ← h₁]

-- Strict inequalities can also be used as non-strict ones:
example (h₁ : a < b) (h₂ : b < c) : a ≤ c := by
grw [h₁, h₂]
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