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pp:2024:scala:l05 [2024/03/29 08:41] tudor.condrea |
pp:2024:scala:l05 [2024/03/31 16:45] (current) tudor.condrea |
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| **5.1.1.** We introduce a carrier class. Modify the type signature so that it allows for animal subtypes. | **5.1.1.** We introduce a carrier class. Modify the type signature so that it allows for animal subtypes. | ||
| <code scala> | <code scala> | ||
| - | class Carrier[T](val content: T) | + | class Carrier[T <: Animal](val content: T) |
| </code> | </code> | ||
| Line 27: | Line 27: | ||
| ==== Contravariance ==== | ==== Contravariance ==== | ||
| - | We introduce a veterinarian class. Consider why this class is contravariant in ''T''. | + | We introduce a veterinarian class. Consider why this class should be contravariant in ''T''. |
| <code scala> | <code scala> | ||
| - | class Vet[-T <: Animal] { | + | class Vet[T <: Animal] { |
| def treat(patient: T): String = { | def treat(patient: T): String = { | ||
| - | s"Can treat $patient" | + | "Can treat " + patient.toString |
| } | } | ||
| } | } | ||