Containers

This package is a collection of various container-like data structures. Currently only SeqDict and SeqSet are included.

Install using lamdera install lamdera/containers.

SeqDict and SeqSet (sequential)

These behave like Dict and Set with some important differences:

• They do not require comparable keys, any equatable* Elm value can be used as a key
• toList returns a list of key-value pairs in insertion order rather than being sorted by comparable keys
• fromList [ ("A", 1), ("B", 2) ] /= fromList [ ("B", 2), ("A", 1) ], use unorderedEquals if you want to check if two SeqDicts or SeqSets are equal regardless of insertion order

This is similar to pzp1997/assoc-list, however unlike assoc-list, SeqDict and SeqSet are backed by a hashmap meaning they have better asymptotic performance. For example insertions are O(log(n)) rather than O(n) and fromList is O(n * log(n)) rather than O(n^2).

^{*Non-equatable Elm values are currently: functions, Bytes, Html, Json.Value, Task, Cmd, Sub, Never, Texture, Shader, and any datastructures containing these types.}

Comparison to other Elm packages

See miniBill's comparison of Elm Dict implementations for a meta-analysis of implementation and performance characteristics.

Attribution

The core implementation for SeqDict and SeqSet was written by Robin Hansen. Thanks to Ambue for sponsoring the work needed to get this integrated into Lamdera!

Additional reading

If you'd like to read about the trade-offs that were made when designing this package, check out this blog post!