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fix non-compiling tut code in tour #982

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Jan 10, 2018
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fix non-compiling tut code in tour #982

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4 changes: 2 additions & 2 deletions _tour/variances.md
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Expand Up @@ -143,8 +143,8 @@ Another example that can help one understand variance is `trait Function1[-T, +R
Assume the similar `Cat`, `Dog`, `Animal` inheritance tree used earlier, plus the following:

```tut
class SmallAnimal extends Animal
class Mouse extends SmallAnimal
abstract class SmallAnimal extends Animal
case class Mouse(name: String) extends SmallAnimal
```

Suppose we're working with functions that accept types of animals, and return the types of food they eat. If we would like a `Cat => SmallAnimal` (because cats eat small animals), but are given a `Animal => Mouse` instead, our program will still work. Intuitively an `Animal => Mouse` will still accept a `Cat` as an argument, because a `Cat` is an `Animal`, and it returns a `Mouse`, which is also an `SmallAnimal`. Since we can safely and invisibly substitute the former for the latter, we can say `Animal => Mouse` is a subtype of `Cat => SmallAnimal`.
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