Fair Warning, I worked with the other for some time, and have been having an out of band convo with him.

One of the things I absolutely HATE about scala is operator overloading - and the excessive abuse of it. I ran into it just now using some library that used ==.

A Case:

List(1,2) == List(1,2); true Array(1,2) == Array(1,2); false

The reason for this is obvious, list implements equals and does a deep compare. While Array.equals is a pointer compare (like how java do).

This would be obvious in Java because that would look like.

ArrayList<> a = ArrayList<Int>(); ArrayList<> b = ArrayList<Int>(); a.equals(b); // equal because it's a value compare

versus

int[] a = new int[5] int[] b = new int[5] a == b; // obviously false because it's a reference compare.

The lack of a universal idea about what == means is pretty dangerous IMO.

*edited for spelling