clarify what the foreach method does here (scala#1027)

martijnhoekstra · jvican · commit 7700d3605db2 · 2018-03-02T11:20:13.000+01:00
Hopefully closes scala#869
diff --git a/_tour/mixin-class-composition.md b/_tour/mixin-class-composition.md
@@ -67,7 +67,7 @@ trait RichIterator extends AbsIterator {
   def foreach(f: T => Unit): Unit = while (hasNext) f(next())
 }
 ```
-Because `RichIterator` is a trait, it doesn't need to implement the abstract members of AbsIterator.
+This trait implements `foreach` by continually calling the provided function `f: T => Unit` on the next element (`next()`) as long as there are further elements (`while (hasNext)`). Because `RichIterator` is a trait, it doesn't need to implement the abstract members of AbsIterator.
 
 We would like to combine the functionality of `StringIterator` and `RichIterator` into a single class.
 

Original file line number	Diff line number	Diff line change
`@@ -67,7 +67,7 @@ trait RichIterator extends AbsIterator {`
`67`	`67`	`def foreach(f: T => Unit): Unit = while (hasNext) f(next())`
`68`	`68`	`}`
`69`	`69`	```
`70`		-Because `RichIterator` is a trait, it doesn't need to implement the abstract members of AbsIterator.
	`70`	+This trait implements `foreach` by continually calling the provided function `f: T => Unit` on the next element (`next()`) as long as there are further elements (`while (hasNext)`). Because `RichIterator` is a trait, it doesn't need to implement the abstract members of AbsIterator.
`71`	`71`
`72`	`72`	We would like to combine the functionality of `StringIterator` and `RichIterator` into a single class.
`73`	`73`