test(library): test new 'obtain' expression in the standard library

library/data/rat/order.lean

@@ -171,8 +171,9 @@ iff.intro
     have H2 : a ≠ b, from ne.symm (assume H', H1 (H' ▸ !sub_self)),
     and.intro (nonneg_of_pos H) H2)
   (assume H : a ≤ b ∧ a ≠ b,
-    have H1 : b - a ≠ 0, from (assume H', and.right H (eq_of_sub_eq_zero H')⁻¹),
-    pos_of_nonneg_of_ne_zero (and.left H) H1)
+    obtain aleb aneb, from H,
+    have H1 : b - a ≠ 0, from (assume H', aneb (eq_of_sub_eq_zero H')⁻¹),
+    pos_of_nonneg_of_ne_zero aleb H1)
 
 theorem le_iff_lt_or_eq (a b : ℚ) : a ≤ b ↔ a < b ∨ a = b :=
 iff.intro

library/data/set/map.lean

@@ -89,9 +89,9 @@ and.intro (injective_of_equiv H1 (and.left H2)) (surjective_of_equiv H1 (and.rig
 
 theorem bijective_compose {g : map b c} {f : map a b} (Hg : bijective g) (Hf: bijective f) :
   bijective (g ∘ f) :=
-and.intro
-  (injective_compose (and.left Hg) (and.left Hf))
-  (surjective_compose (and.right Hg) (and.right Hf))
+obtain Hg₁ Hg₂, from Hg,
+obtain Hf₁ Hf₂, from Hf,
+and.intro (injective_compose Hg₁ Hf₁) (surjective_compose Hg₂ Hf₂)
 
 /- left inverse -/
 

library/logic/connectives.lean

@@ -85,12 +85,12 @@ iff.intro (λH, and.swap H) (λH, and.swap H)
 
 theorem and.assoc : (a ∧ b) ∧ c ↔ a ∧ (b ∧ c) :=
 iff.intro
-  (assume H, and.intro
-    (and.elim_left (and.elim_left H))
-    (and.intro (and.elim_right (and.elim_left H)) (and.elim_right H)))
-  (assume H, and.intro
-    (and.intro (and.elim_left H) (and.elim_left (and.elim_right H)))
-    (and.elim_right (and.elim_right H)))
+  (assume H,
+   obtain [Ha Hb] Hc, from H,
+   and.intro Ha (and.intro Hb Hc))
+  (assume H,
+   obtain Ha Hb Hc, from H,
+   and.intro (and.intro Ha Hb) Hc)
 
 theorem and_true (a : Prop) : a ∧ true ↔ a :=
 iff.intro (assume H, and.left H) (assume H, and.intro H trivial)