ocaml-containers

What is containers?

• A usable, reasonably well-designed library that extends OCaml's standard library (in core/, packaged under containers in ocamlfind. Modules are totally independent and are prefixed with CC (for "containers-core" or "companion-cube" because I'm megalomaniac). This part should be usable and should work. For instance, CCList contains functions and lists including safe versions of map and append. It also provides a drop-in replacement to the standard library, in the module Containers (intended to be opened, replaces some stdlib modules with extended ones)
• Several small additional libraries that complement it:
  • containers.data with additional data structures that don't have an equivalent in the standard library;
  • containers.io (deprecated)
  • containers.iter with list-like and tree-like iterators;
  • containers.string (in directory string) with a few packed modules that deal with strings (Levenshtein distance, KMP search algorithm, and a few naive utils). Again, modules are independent and sometimes parametric on the string and char types (so they should be able to deal with your favorite unicode library).
• A sub-library with complicated abstractions, containers.advanced (with a LINQ-like query module, batch operations using GADTs, and others).
• Utilities around the unix library in containers.unix (mainly to spawn sub-processes)
• A bigstring module using bigarray in containers.bigarray
• A lightweight S-expression printer and streaming parser in containers.sexp
• A library using Lwt, containers.lwt. Currently only contains experimental, unstable stuff.
• Random stuff, with NO GUARANTEE of even being barely usable or tested, in other dirs (mostly misc but also lwt and threads). It's where I tend to write code when I want to test some idea, so half the modules (at least) are unfinished or don't really work.

Some of the modules have been moved to their own repository (e.g. sequence, gen, qcheck) and are on opam for great fun and profit.

Change Log

See this file.

Finding help

• new: Mailing List on the forge; the address is containers-users@lists.forge.ocamlcore.org
• the github wiki
• on IRC, ask companion_cube on #ocaml
• (experimental, might not exist forever)

Use

You can either build and install the library (see Build), or just copy files to your own project. The last solution has the benefits that you don't have additional dependencies nor build complications (and it may enable more inlining). Since modules have a friendly license and are mostly independent, both options are easy.

In a toplevel, using ocamlfind:

# #use "topfind";;
# #require "containers";;
# CCList.flat_map;;
- : ('a -> 'b list) -> 'a list -> 'b list = <fun>
# open Containers;;  (* optional *)
# List.flat_map ;;
- : ('a -> 'b list) -> 'a list -> 'b list = <fun>

If you have comments, requests, or bugfixes, please share them! :-)

License

This code is free, under the BSD license.

The logo (media/logo.png) is CC-SA3 wikimedia.

Contents

The design is mostly centered around polymorphism rather than functors. Such structures comprise (some modules in misc/, some other in core/):

Core Modules (extension of the standard library)

the core library, containers, now depends on cppo and base-bytes (provided by ocamlfind).

Documentation here.

• CCHeap, a purely functional heap structure
• CCVector, a growable array (pure OCaml, no C) with mutability annotations
• CCList, functions on lists, including tail-recursive implementations of map and append and many other things
• CCArray, utilities on arrays and slices
• CCHashtbl, CCMap extensions of the standard modules Hashtbl and Map
• CCInt
• CCString (basic string operations)
• CCPair (cartesian products)
• CCOpt (options, very useful)
• CCFun (function combinators)
• CCBool
• CCFloat
• CCOrd (combinators for total orderings)
• CCRandom (combinators for random generators)
• CCPrint (printing combinators)
• CCHash (hashing combinators)
• CCError (monadic error handling, very useful)
• CCIO, basic utilities for IO (channels, files)

Containers.data

• CCBitField, bitfields embedded in integers
• CCBloom, a bloom filter
• CCCache, memoization caches, LRU, etc.
• CCFlatHashtbl, a flat (open-addressing) hashtable functorial implementation
• CCTrie, a prefix tree
• CCHashTrie, a map where keys are hashed and put in a trie by hash
• CCMultimap and CCMultiset, functors defining persistent structures
• CCFQueue, a purely functional double-ended queue structure
• CCBV, mutable bitvectors
• CCHashSet, mutable set
• CCPersistentHashtbl and CCPersistentArray, a semi-persistent array and hashtable (similar to persistent arrays)
• CCMixmap, CCMixtbl, CCMixset, containers of universal types (heterogenous containers)
• CCRingBuffer, a double-ended queue on top of an array-like structure, with batch operations
• CCIntMap, map specialized for integer keys based on Patricia Trees, with fast merges
• CCHashconsedSet, a set structure with sharing of sub-structures
• CCGraph, a small collection of graph algorithms
• CCBitField, a type-safe implementation of bitfields that fit in int
• CCWBTree, a weight-balanced tree, implementing a map interface
• CCRAL, a random-access list structure, with O(1) cons/hd/tl and O(ln(n)) access to elements by their index.

Containers.io

deprecated, CCIO is now a core module. You can still install it and depend on it but it contains no useful module.

Containers.unix

• CCUnix, utils for Unix

Containers.sexp

A small S-expression library.

• CCSexp, a small S-expression library

Containers.iter

Iterators:

• CCKList, a persistent iterator structure (akin to a lazy list, without memoization)
• CCKTree, an abstract lazy tree structure

String

See doc.

In the module Containers_string:

• Levenshtein: edition distance between two strings
• KMP: Knuth-Morris-Pratt substring algorithm

Advanced

See doc.

In the module Containers_advanced:

• CCLinq, high-level query language over collections
• CCCat, a few categorical structures
• CCBatch, to combine operations on collections into one traversal

Thread

In the library containers.thread, for preemptive system threads:

• CCFuture, a set of tools for preemptive threading, including a thread pool, monadic futures, and MVars (concurrent boxes)
• CCLock, values protected by locks
• CCSemaphore, a simple implementation of semaphores
• CCThread basic wrappers for Thread

Misc

See doc. This list is not necessarily up-to-date.

• AbsSet, an abstract Set data structure, a bit like LazyGraph.
• Automaton, CSM, state machine abstractions
• Bij, a GADT-based bijection language used to serialize/deserialize your data structures
• Hashset, a polymorphic imperative set on top of PHashtbl
• LazyGraph, a lazy graph structure on arbitrary (hashable+eq) types, with basic graph functions that work even on infinite graphs, and printing to DOT.
• PHashtbl, a polymorphic hashtable (with open addressing)
• RoseTree, a tree with an arbitrary number of children and its associated zipper
• SmallSet, a sorted list implementation behaving like a set.
• UnionFind, a functorial imperative Union-Find structure
• Univ, a universal type encoding with affectation

Others

• containers.lwt contains Lwt-related modules (experimental)

There is a QuickCheck-like library called QCheck (now in its own repo).

Incoming (Breaking) Changes

the following breaking changes are likely to occur for the next release (they can still be discussed, of course):

• moving containers.lwt into its own repository and opam package
• moving containers.misc into its own repository and opam package (improving the average quality of containers!)
• aliasing and deprecating CCList.split (confusion with List.split)

already in git (but can be reverted if needed):

• change exceptions in CCVector
• change signature of CCDeque.of_seq (remove optional argument)
• heavily refactor CCLinq in containers.advanced. If you use this module, you will most likely have to change your code (into simpler code, hopefully).
• RAL in containers.misc moved to containers.data as CCRAL, and is getting improved on the way

Build

You will need OCaml >= 4.01.0.

Via opam

The prefered way to install is through opam.

$ opam install containers

From Sources

On the branch master you will need oasis to build the library. On the branch stable it is not necessary.

$ make

To build and run tests (requires oUnit, qtest, and qcheck):

$ opam install oUnit qtest qcheck
$ ./configure --enable-tests
$ make test

To build the small benchmarking suite (requires benchmark):

$ opam install benchmark
$ make bench
$ ./benchs.native

Contributing

PRs on github are welcome (patches by email too, if you prefer so).

A few guidelines:

• no dependencies between basic modules (even just for signatures);
• add @since tags for new functions;
• add tests if possible (using qtest).

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