feat(library/standard): add namespace 'pair'

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

library/standard/pair.lean

@@ -3,6 +3,7 @@
 -- Author: Leonardo de Moura
 import logic
 
+namespace pair
 inductive pair (A : Type) (B : Type) : Type :=
 | mk_pair : A → B → pair A B
 
@@ -25,10 +26,12 @@ section
   theorem pair_ext (p : pair A B) : mk_pair (fst p) (snd p) = p
   := pair_rec (λ x y, refl (mk_pair x y)) p
 end
-instance pair_inhabited
+
+instance pair.pair_inhabited
 
 precedence `×`:30
 infixr × := pair
 
 -- notation for n-ary tuples
 notation `(` h `,` t:(foldl `,` (e r, mk_pair r e) h) `)` := t
+end

tests/lean/run/class1.lean

@@ -1,5 +1,6 @@
 import standard
 using num
+using pair
 
 definition H : inhabited (Bool × num × (num → num)) := _
 

tests/lean/run/class2.lean

@@ -1,5 +1,6 @@
 import standard
 using num
+using pair
 
 theorem H {A B : Type} (H1 : inhabited A) : inhabited (Bool × A × (B → num))
 := _

tests/lean/run/class3.lean

@@ -1,5 +1,6 @@
 import standard
 using num
+using pair
 
 section
   parameter {A : Type}

tests/lean/run/class6.lean

@@ -1,4 +1,5 @@
 import standard
+using pair
 
 inductive t1 : Type :=
 | mk1 : t1

tests/lean/run/ptst.lean

@@ -1,4 +1,5 @@
 import standard
+using pair
 
 -- Test tuple notation
 check (3, false, 1, true)