Why is there no lengthCompare method in Scala Set?

Question

There is a lengthCompare method in Scala Seq that returns a comparison between the length of the Seq and the given Int without calculating the length of the Seq .

It is implemented in the SeqLike as follows:

 /** Compares the length of this $coll to a test value. * * @param len the test value that gets compared with the length. * @return A value `x` where * {{{ * x < 0 if this.length < len * x == 0 if this.length == len * x > 0 if this.length > len * }}} * The method as implemented here does not call `length` directly; its running time * is `O(length min len)` instead of `O(length)`. The method should be overwritten * if computing `length` is cheap. */ def lengthCompare(len: Int): Int = { if (len < 0) 1 else { var i = 0 val it = iterator while (it.hasNext) { if (i == len) return if (it.hasNext) 1 else 0 it.next() i += 1 } i - len } } 

Since this implementation only requires an iterator , why is it not defined in IterableLike ?

This will make it available in the collections of Seq , Set and Map .

Answer 1

The new Scala 2.13 collection, released just yesterday, has one, see here . The simple reason is that many of the things in the Scala collections were not what they should be, which is now fixed. The fact that it exists in the new version indicates that it was not an active choice to exclude it earlier.