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More precise wording in abstract-type-members.md #1287

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6 changes: 3 additions & 3 deletions _tour/abstract-type-members.md
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ abstract class SeqBuffer extends Buffer {
def length = element.length
}
```
Notice how we can use yet another abstract `type U` as an upper-type-bound. This `class SeqBuffer` allows us to store only sequences in the buffer by stating that type `T` has to be a subtype of `Seq[U]` for a new abstract type `U`.
Notice how we can use yet another abstract type `U` in the specification of an upper-type-bound for `T`. This `class SeqBuffer` allows us to store only sequences in the buffer by stating that type `T` has to be a subtype of `Seq[U]` for a new abstract type `U`.

Traits or [classes](classes.html) with abstract type members are often used in combination with anonymous class instantiations. To illustrate this, we now look at a program which deals with a sequence buffer that refers to a list of integers:

Expand All @@ -53,7 +53,7 @@ val buf = newIntSeqBuf(7, 8)
println("length = " + buf.length)
println("content = " + buf.element)
```
Here the factory `newIntSeqBuf` uses an anonymous class implementation of `IntSeqBuf` (i.e. `new IntSeqBuffer`), setting `type T` to a `List[Int]`.
Here the factory `newIntSeqBuf` uses an anonymous class implementation of `IntSeqBuf` (i.e. `new IntSeqBuffer`) to set the abstract type `T` to the concrete type `List[Int]`.

It is also possible to turn abstract type members into type parameters of classes and vice versa. Here is a version of the code above which only uses type parameters:

Expand All @@ -75,4 +75,4 @@ println("length = " + buf.length)
println("content = " + buf.element)
```

Note that we have to use [variance annotations](variances.html) here (`+T <: Seq[U]`) in order to hide the concrete sequence implementation type of the object returned from method `newIntSeqBuf`. Furthermore, there are cases where it is not possible to replace abstract types with type parameters.
Note that we have to use [variance annotations](variances.html) here (`+T <: Seq[U]`) in order to hide the concrete sequence implementation type of the object returned from method `newIntSeqBuf`. Furthermore, there are cases where it is not possible to replace abstract type members with type parameters.