# \[ANN\] containers 3.0 **URL:** \ **Category:** Ecosystem\ **Tags:** announce\ **Created:** [August 4, 2020, 1:46pm UTC](https://discuss.ocaml.org/t/ann-containers-3-0/6194 "2020-08-04T13:46:07Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![c-cube](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/c-cube/32/1727_2.png) [@c-cube](https://discuss.ocaml.org/u/c-cube)\ **Post date:** [August 4, 2020, 1:46pm UTC](https://discuss.ocaml.org/t/ann-containers-3-0/6194/1 "2020-08-04T13:46:07Z")
Dear y’all and all y’all’s, I’m happy to announce, on behalf of containers’ contributors, the release of [containers 3.0](https://github.com/c-cube/ocaml-containers/releases/tag/v3.0). API documentation can be found [here](https://c-cube.github.io/ocaml-containers/3.0/). Containers is a BSD-licensed standard library _extension_ [1] that aims at being lightweight, convenient, modular, portable, and only pay for what you use; that includes compatibility with OCaml \>= 4.03. This is the second major update in 7 years of existence, following semantic versioning. Release 3.0 was the opportunity to clean up some inconsistencies (in printers, among others), to focus on the standard `Seq.t` type, and to split some sub-libraries into their own packages (`containers-thread` and `containers-data` respectively). The hope is that the new version is more consistent, lightweight, and pleasant to use. I want to thank all contributors for their hard work, and in particular [Fardale](https://github.com/FardaleM). [1]: as in, containers extends the stdlib and does not intend to replace it. ## Overview of breaking changes (this is extracted from [the readme’s migration section](https://github.com/c-cube/ocaml-containers/blob/master/README.md#to-30)) 1. The biggest change is that some sub-libraries have been either turned into their own packages (`containers-thread`, `containers-data`), deleted (`containers.iter`),or merged elsewhere (`containers.sexp`). This means that if use these libraries you will have to edit your `dune`/`_oasis`/`opam` files. - if you use `containers.sexp` (i.e. the `CCSexp` module), it now lives in `containers` itself. - if you used anything in `containers.data`, you need to depend on the `containers-data` package now. 1. Another large change is the removal (at last!) of functions deprecated in 2.8, related to the spread of `Seq.t` as the standard iterator type. Functions like `CCVector.of_seq` now operate on this standard `Seq.t` type, and old-time iteration based on [iter](https://github.com/c-cube/iter) is now named `of_iter`, `to_iter`, etc. Here you need to change you code, possibly using search and replace. Thankfully, the typechecker should guide you. 1. `Array_slice` and `String.Sub` have been removed to simplify the code and `String` more lightweight. There is no replacement at the moment. Please tell us if you need this to be turned into a sub-library. 2. Renaming of some functions into more explicit/clear names. Examples: - `CCVector.shrink` is now `CCVector.truncate` - `CCVector.remove` is now `CCVector.remove_unordered`, to be contrasted with the new `CCVector.remove_and_shift`. - `CCPair.map_fst` and `map_snd` now transform a tuple into another tuple by modify the first (resp. second) element. 1. All the collection pretty-printers now take their separator/start/stop optional arguments as `unit printer` (i.e. `Format.formatter -> unit -> unit` functions) rather than strings. This gives the caller better control over the formatting of lists, arrays, queues, tables, etc. 2. Removal of many deprecated functions. ---
**Author:** ![orbitz](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/orbitz/32/110_2.png) [@orbitz](https://discuss.ocaml.org/u/orbitz)\ **Post date:** [August 4, 2020, 3:53pm UTC](https://discuss.ocaml.org/t/ann-containers-3-0/6194/2 "2020-08-04T15:53:10Z")
Awesome! Thank you, I’m a big user of containers and appreciate the hard work by everyone.