Sync

Task/Constrained-genericity/Haskell/constrained-genericity-7.hs

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+import Utils        # From the UniLib package to get the Class class.
+
+class Eatable:Class()
+end
+
+class Fish:Eatable(name)
+    method eat(); write("Eating "+name); end
+end
+
+class Rock:Class(name)
+    method eat(); write("Eating "+name); end
+end
+
+class FoodBox(A)
+initially
+    every item := !A do if "Eatable" == item.Type() then next else bad := "yes"
+    return /bad
+end
+
+procedure main()
+    if FoodBox([Fish("salmon")]) then write("Edible") else write("Inedible")
+    if FoodBox([Rock("granite")]) then write("Edible") else write("Inedible")
+end