diff --git a/examples/lean/dep_if.lean b/examples/lean/dep_if.lean index 3dc537138..71f0c9975 100644 --- a/examples/lean/dep_if.lean +++ b/examples/lean/dep_if.lean @@ -32,13 +32,16 @@ theorem then_simp (A : TypeU) (c : Bool) (r : A) (t : c → A) (e : ¬ c → A) in by simp -- Given H : c, (dep_if c t e) = t H -theorem dep_if_true {A : TypeU} (c : Bool) (t : c → A) (e : ¬ c → A) (H : c) : dep_if c t e = t H +theorem dep_if_elim_then {A : TypeU} (c : Bool) (t : c → A) (e : ¬ c → A) (H : c) : dep_if c t e = t H := let s1 : (λ r, (∀ Hc : c, r = t Hc) ∧ (∀ Hnc : ¬ c, r = e Hnc)) = (λ r, r = t H) := funext (λ r, then_simp A c r t e H) in calc dep_if c t e = ε (nonempty_resolve t e) (λ r, (∀ Hc : c, r = t Hc) ∧ (∀ Hnc : ¬ c, r = e Hnc)) : refl (dep_if c t e) ... = ε (nonempty_resolve t e) (λ r, r = t H) : { s1 } ... = t H : eps_singleton (nonempty_resolve t e) (t H) +theorem dep_if_true {A : TypeU} (t : true → A) (e : ¬ true → A) : dep_if true t e = t trivial +:= dep_if_elim_then true t e trivial + theorem else_simp (A : TypeU) (c : Bool) (r : A) (t : c → A) (e : ¬ c → A) (H : ¬ c) : (∀ Hc : c, r = t Hc) ∧ (∀ Hnc : ¬ c, r = e Hnc) ↔ r = e H := let s1 : (∀ Hc : c, r = t Hc) ↔ true @@ -52,13 +55,16 @@ theorem else_simp (A : TypeU) (c : Bool) (r : A) (t : c → A) (e : ¬ c → A) in by simp -- Given H : ¬ c, (dep_if c t e) = e H -theorem dep_if_false {A : TypeU} (c : Bool) (t : c → A) (e : ¬ c → A) (H : ¬ c) : dep_if c t e = e H +theorem dep_if_elim_else {A : TypeU} (c : Bool) (t : c → A) (e : ¬ c → A) (H : ¬ c) : dep_if c t e = e H := let s1 : (λ r, (∀ Hc : c, r = t Hc) ∧ (∀ Hnc : ¬ c, r = e Hnc)) = (λ r, r = e H) := funext (λ r, else_simp A c r t e H) in calc dep_if c t e = ε (nonempty_resolve t e) (λ r, (∀ Hc : c, r = t Hc) ∧ (∀ Hnc : ¬ c, r = e Hnc)) : refl (dep_if c t e) ... = ε (nonempty_resolve t e) (λ r, r = e H) : { s1 } ... = e H : eps_singleton (nonempty_resolve t e) (e H) +theorem dep_if_false {A : TypeU} (t : false → A) (e : ¬ false → A) : dep_if false t e = e trivial +:= dep_if_elim_else false t e trivial + import cast theorem dep_if_congr {A : TypeM} (c1 c2 : Bool) @@ -85,7 +91,7 @@ pop_scope -- can reduce the dependent-if to a regular if theorem dep_if_if {A : TypeU} (c : Bool) (t e : A) : dep_if c (λ Hc, t) (λ Hn, e) = if c then t else e := or_elim (em c) - (assume Hc : c, calc dep_if c (λ Hc, t) (λ Hn, e) = (λ Hc, t) Hc : dep_if_true _ _ _ Hc + (assume Hc : c, calc dep_if c (λ Hc, t) (λ Hn, e) = (λ Hc, t) Hc : dep_if_elim_then _ _ _ Hc ... = if c then t else e : by simp) - (assume Hn : ¬ c, calc dep_if c (λ Hc, t) (λ Hn, e) = (λ Hn, e) Hn : dep_if_false _ _ _ Hn + (assume Hn : ¬ c, calc dep_if c (λ Hc, t) (λ Hn, e) = (λ Hn, e) Hn : dep_if_elim_else _ _ _ Hn ... = if c then t else e : by simp)