While scrolling around, I found that Map.new/2 uses :lists.reverse/1 after the transformation on the enumerable is completed. I wonder if that is actually needed. I benchmarked the implementation against one without :lists.reverse/1 with benchee. The results are that it doesn’t slow down the function, but memory usage increases. I guess one reason to use :lists.reverse/1 is in order to handle duplicate keys just as Map.new/1 does. Is that the reason why :lists.reverse/1 is used?
