2016 Update

Task/Constrained-genericity/Fortran/constrained-genericity.f

@@ -0,0 +1,42 @@
+module cg
+    implicit none
+
+    type, abstract :: eatable
+    end type eatable
+
+    type, extends(eatable) :: carrot_t
+    end type carrot_t
+
+    type :: brick_t; end type brick_t
+
+    type :: foodbox
+	class(eatable), allocatable :: food
+    contains
+        procedure, public :: add_item => add_item_fb
+    end type foodbox
+
+contains
+
+    subroutine add_item_fb(this, f)
+        class(foodbox), intent(inout) :: this
+        class(eatable), intent(in)    :: f
+        allocate(this%food, source=f)
+    end subroutine add_item_fb
+end module cg
+
+
+program con_gen
+    use cg
+    implicit none
+
+    type(carrot_t) :: carrot
+    type(brick_t)  :: brick
+    type(foodbox)  :: fbox
+
+    ! Put a carrot into the foodbox
+    call fbox%add_item(carrot)
+
+    ! Try to put a brick in - results in a compiler error
+    call fbox%add_item(brick)
+
+end program con_gen

Task/Constrained-genericity/J/constrained-genericity-1.j

@@ -5,10 +5,10 @@ isEdible=:3 :0
 
 coclass'FoodBox'
 create=:3 :0
-  assert isEdible_Connoisseur_ type=:y
   collection=: 0#y
 )
 add=:3 :0"0
-  'inedible' assert type e. copath y
+  'inedible' assert isEdible_Connoisseur_ y
   collection=: collection, y
+  EMPTY
 )

Task/Constrained-genericity/J/constrained-genericity-3.j

@@ -1,4 +1,4 @@
-   lunch=:(<'Apple') conew 'FoodBox'
+   lunch=:'' conew 'FoodBox'
    a1=: conew 'Apple'
    a2=: conew 'Apple'
    add__lunch a1

Task/Constrained-genericity/Perl-6/constrained-genericity-1.pl6

@@ -2,8 +2,8 @@ subset Eatable of Any where { .^can('eat') };
 
 class Cake { method eat() {...} }
 
-role FoodBox[Eatable ::T] {
-    has T %.foodbox;
+role FoodBox[Eatable] {
+    has %.foodbox;
 }
 
 class Yummy does FoodBox[Cake] { }      # composes correctly

Task/Constrained-genericity/Ruby/constrained-genericity.rb

@@ -0,0 +1,18 @@
+class Foodbox
+  def initialize (*food)
+    raise ArgumentError, "food must be eadible" unless  food.all?{|f| f.respond_to?(:eat)}
+    @box = food
+  end
+end
+
+class Fruit
+  def eat; end
+end
+
+class Apple < Fruit; end
+
+p Foodbox.new(Fruit.new, Apple.new)
+# => #<Foodbox:0x00000001420c88 @box=[#<Fruit:0x00000001420cd8>, #<Apple:0x00000001420cb0>]>
+
+p Foodbox.new(Apple.new, "string can't eat")
+# => test1.rb:3:in `initialize': food must be eadible (ArgumentError)