[pharmakom]

Immutable structures cannot be cyclical. Maybe I’m missing something?

[Jeaye]

Exactly as nlitened mentioned, Clojure has a few difference reference types, which are boxes that hold pointers to more immutable values. The values within those boxes can be changed transactionally. This allows for cyclical references.

[nlitened]

In Clojure, the data structures may usually contain references to mutable cells, which in turn may form cycles.