The submodule Array is a replacement for OCaml's standard Array module, where an array is implemented as an ephemeral sequence.

The submodule List is a replacement for OCaml's standard List module, where a list is implemented as a persistent sequence.

The submodule Queue is a replacement for OCaml's standard Queue module, where a queue is implemented as an ephemeral sequence. Elements are enqueued at the back end of the sequence and dequeued at the front end.

The submodule Stack is a replacement for OCaml's standard Stack module, where a stack is implemented as an ephemeral sequence. Elements are pushed and popped at the front end of the sequence.