`unordered-containers` Introduction¶

The unordered-containers package provides implementations of various hash-based immutable data structures.

Some of the data structures provided by this package have a very large API surface (for better or worse). The docs here focus on the most common functions which should be more than enough to get you started. Once you know the basics, or if you’re looking for a specific function, you can head over to the unordered-containers Haddocks to check out the full API documentation!

Provided Data Structures¶

Hash Sets: unordered, non-duplicated elements
Hash Maps: unordered maps from keys to values (aka. dictionaries)

Looking for more resources?¶

If you’ve worked your way through the documentation here and you’re looking for more examples or tutorials you should check out:

haskell-lang.org’s containers tutorial, its focused on the ordered containers library but provides some useful examples.
Learn You a Haskell “Modules” chapter

Installing and using the `unordered-containers` package¶

Version Requirements¶

All of the examples here should work for all recent versions of the package.

Importing modules¶

All of the modules in unordered-containers should be imported qualified since they use names that conflict with the standard Prelude.

import qualified Data.HashSet as HashSet
import qualified Data.HashMap.Strict as HashMap

In GHCi¶

Start the GHCi REPL with ghci, cabal repl, or stack ghci. Once the REPL is loaded, import the modules you want using the import statements above and you’re good to go!

In a Cabal or Stack project¶

Add unordered-containers to the build-depends: stanza for your library, executable, or test-suite:

library
    build-depends:
        base >= 4.3 && < 5,
        unordered-containers >= 0.2.7 && < 0.3

and import any modules you need in your Haskell source files.

unordered-containers Introduction¶