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Project-declaredLean 4.8.0 · mathlib@b5eba5954288

Pr le pr enrich

Prob.pr_le_pr_enrich

Plain-language statement

pr_mono when the right side is enriched

Exact Lean statement

lemma pr_le_pr_enrich {f : Prob α} {g : α → Prob β} {p : α × β → Prop} {i : α → Prop}
    (ip : ∀ x y, f.prob x ≠ 0 → (g x).prob y ≠ 0 → i x → p (x,y)) :
    f.pr i ≤ (f >>= λ x ↦ Prod.mk x <$> g x).pr p

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
lemma pr_le_pr_enrich {f : Prob α} {g : α  Prob β} {p : α × β  Prop} {i : α  Prop}    (ip :  x y, f.prob x  0  (g x).prob y  0  i x  p (x,y)) :    f.pr i  (f >>= λ x  Prod.mk x <$> g x).pr p := by  simp only [pr_bind]; apply exp_mono; intro x fx; by_cases ix : i x  · apply le_of_eq; simp only [ix, if_true]; refine (pr_eq_one.mpr ?_).symm; intro x',y pxy    contrapose pxy; simp only [not_not, prob_map]; rw [pr_eq_zero]; intro y' n    contrapose pxy; simp only [Prod.mk.injEq, not_and, not_forall, not_not, exists_prop] at pxy     simp only [pxy.1, pxy.2] at n ; apply ip x y fx n ix  · simp only [ix, if_false]; exact pr_nonneg
Project
debate
License
Apache-2.0
Commit
de3a6e500ae1
Source
Prob/Cond.lean:276-284

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