# Documentation

## Mathlib.Tactic.PushNeg

theorem Mathlib.Tactic.PushNeg.not_and_eq (p : Prop) (q : Prop) :
(¬(p q)) = (p¬q)
theorem Mathlib.Tactic.PushNeg.not_or_eq (p : Prop) (q : Prop) :
(¬(p q)) = (¬p ¬q)
theorem Mathlib.Tactic.PushNeg.not_forall_eq {α : Sort u_1} (s : αProp) :
(¬∀ (x : α), s x) = ∃ (x : α), ¬s x
theorem Mathlib.Tactic.PushNeg.not_exists_eq {α : Sort u_1} (s : αProp) :
(¬∃ (x : α), s x) = ∀ (x : α), ¬s x
theorem Mathlib.Tactic.PushNeg.not_implies_eq (p : Prop) (q : Prop) :
(¬(pq)) = (p ¬q)
theorem Mathlib.Tactic.PushNeg.not_ne_eq {α : Sort u_1} (x : α) (y : α) :
(¬x y) = (x = y)
theorem Mathlib.Tactic.PushNeg.not_iff (p : Prop) (q : Prop) :
(¬(p q)) = (p ¬q ¬p q)
theorem Mathlib.Tactic.PushNeg.not_le_eq {β : Type u} [] (a : β) (b : β) :
(¬a b) = (b < a)
theorem Mathlib.Tactic.PushNeg.not_lt_eq {β : Type u} [] (a : β) (b : β) :
(¬a < b) = (b a)
theorem Mathlib.Tactic.PushNeg.not_ge_eq {β : Type u} [] (a : β) (b : β) :
(¬a b) = (a < b)
theorem Mathlib.Tactic.PushNeg.not_gt_eq {β : Type u} [] (a : β) (b : β) :
(¬a > b) = (a b)
theorem Mathlib.Tactic.PushNeg.not_nonempty_eq {γ : Type u_1} (s : Set γ) :
(¬s.Nonempty) = (s = )
theorem Mathlib.Tactic.PushNeg.ne_empty_eq_nonempty {γ : Type u_1} (s : Set γ) :
(s ) = s.Nonempty
theorem Mathlib.Tactic.PushNeg.empty_ne_eq_nonempty {γ : Type u_1} (s : Set γ) :
( s) = s.Nonempty

Make push_neg use not_and_or rather than the default not_and.

Push negations at the top level of the current expression.

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Recursively push negations at the top level of the current expression. This is needed to handle e.g. triple negation.

Common entry point to push_neg as a conv.

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Push negations into the conclusion of an expression. For instance, an expression ¬ ∀ x, ∃ y, x ≤ y will be transformed by push_neg into ∃ x, ∀ y, y < x. Variable names are conserved. This tactic pushes negations inside expressions. For instance, given a hypothesis

| ¬ ∀ ε > 0, ∃ δ > 0, ∀ x, |x - x₀| ≤ δ → |f x - y₀| ≤ ε)


writing push_neg will turn the target into

| ∃ ε, ε > 0 ∧ ∀ δ, δ > 0 → (∃ x, |x - x₀| ≤ δ ∧ ε < |f x - y₀|),


(The pretty printer does not use the abbreviations ∀ δ > 0 and ∃ ε > 0 but this issue has nothing to do with push_neg).

Note that names are conserved by this tactic, contrary to what would happen with simp using the relevant lemmas.

This tactic has two modes: in standard mode, it transforms ¬(p ∧ q) into p → ¬q, whereas in distrib mode it produces ¬p ∨ ¬q. To use distrib mode, use set_option push_neg.use_distrib true.

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Execute push_neg as a conv tactic.

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The syntax is #push_neg e, where e is an expression, which will print the push_neg form of e.

#push_neg understands local variables, so you can use them to introduce parameters.

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Execute main loop of push_neg at the main goal.

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Execute main loop of push_neg at a local hypothesis.

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Push negations into the conclusion of a hypothesis. For instance, a hypothesis h : ¬ ∀ x, ∃ y, x ≤ y will be transformed by push_neg at h into h : ∃ x, ∀ y, y < x. Variable names are conserved. This tactic pushes negations inside expressions. For instance, given a hypothesis

h : ¬ ∀ ε > 0, ∃ δ > 0, ∀ x, |x - x₀| ≤ δ → |f x - y₀| ≤ ε)


writing push_neg at h will turn h into

h : ∃ ε, ε > 0 ∧ ∀ δ, δ > 0 → (∃ x, |x - x₀| ≤ δ ∧ ε < |f x - y₀|),


(The pretty printer does not use the abbreviations ∀ δ > 0 and ∃ ε > 0 but this issue has nothing to do with push_neg).

Note that names are conserved by this tactic, contrary to what would happen with simp using the relevant lemmas. One can also use this tactic at the goal using push_neg, at every hypothesis and the goal using push_neg at * or at selected hypotheses and the goal using say push_neg at h h' ⊢ as usual.

This tactic has two modes: in standard mode, it transforms ¬(p ∧ q) into p → ¬q, whereas in distrib mode it produces ¬p ∨ ¬q. To use distrib mode, use set_option push_neg.use_distrib true.

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