Constrained genericity: Difference between revisions

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 let your_box = FloatBox.make_box_from_list [2.3; 4.5]</lang>
 Unfortunately, it is kind of cumbersome in that, for every type parameter we want to use for this generic type, we will have to explicitly create a module for the resulting type (i.e. <tt>BananaBox</tt>, <tt>FloatBox</tt>). And the operations on that resulting type (i.e. <tt>make_box_from_list</tt>) are tied to each specific module.
+=={{header|Sather}}==
+<lang sather>abstract class $EDIBLE is
+  eat;
+end;
+class FOOD < $EDIBLE is
+  readonly attr name:STR;
+  eat is
+    #OUT + "eating " + self.name + "\n";
+  end;
+  create(name:STR):SAME is
+    res ::= new;
+    res.name := name;
+    return res;
+  end;
+end;
+class CAR is
+  readonly attr name:STR;
+  create(name:STR):SAME is
+    res ::= new;
+    res.name := name;
+    return res;
+  end;
+end;
+class FOODBOX{T < $EDIBLE} is
+  private attr list:LLIST{T};
+  create:SAME is
+    res ::= new;
+    res.list := #;
+    return res;
+  end;
+  add(c :T) is
+    self.list.insert_back(c);
+  end;
+  elt!:T is loop yield self.list.elt!; end; end;
+end;
+class MAIN is
+  main is
+    box  ::= #FOODBOX{FOOD}; -- ok
+    box.add(#FOOD("Banana"));
+    box.add(#FOOD("Amanita Muscaria"));
+    box2 ::= #FOODBOX{CAR};  -- not ok
+    box2.add(#CAR("Punto")); -- but compiler let it pass!
+    -- eat everything
+    loop box.elt!.eat; end;
+  end;
+end;</lang>
+The GNU Sather compiler v1.2.3 let the "box2" pass, even though it shouldn't. Read e.g. [http://www.gnu.org/software/sather/docs-1.2/tutorial/parameterized1751.html this tutorial's section]
 =={{header|Scala}}==