You are correct. But in FP, we understand immutability differently, so it becomes very painful to watch structural equivalence of the following variables: clas

You are correct. But in FP, we understand immutability differently, so it becomes very painful to watch structural equivalence of the following variables: class Foo { var x = 0 } let a = [Foo(), Foo(), Foo()] var b = a a[0].x = 1 var c = b // [0].x == 1 ;( let d = a // [0].x == 1 ;(