Pointers being symmetric was the point of his analogy. The asymmetry shows up when the setter is pure, returning a new version of the record instead of mutatin

Pointers being symmetric was the point of his analogy. The asymmetry shows up when the setter is pure, returning a new version of the record instead of mutating it (as is the case in Haskell). A getter is simple: x = s.foo.bar; As is an impure setter: s.foo.bar = y; But a non-mutating setter is a bit more work: Foo foo2 = s.foo; foo2.bar = y; S s2 = s; s2.foo = foo2;