Statically type safe persistent/immutable/functional data structures for Go.
Inspired by Clojures data structures and the work done in Pyrsistent for Python.
This is an experiment in how close to generics that code generation can take you. There's currently a vector, a slice, a map and a set implemented.
What's a persistent data structure?
Despite their name persistent data structures usually don't refer to data structures stored on disk. Instead they are immutable data structures which are copy-on-write. Eg. whenever you mutate a persistent data structure a new one is created that contains the data in the original plus the mutation while the original is left untouched.
To make this reasonably efficient, "structural sharing" is used between the data structures. Here's a good introduction to how this is done in Clojure: http://hypirion.com/musings/understanding-persistent-vector-pt-1
Installation
go get github.com/tobgu/peds/cmd/peds
Usage
Generate statically type safe code for persistent data structures.
USAGE
peds
FLAGS EXAMPLE
-file path/to/file.go
-imports import1;import2
-maps Map1<int,string>;Map2<float,int>
-pkg package_name
-sets Set1<int>
-vectors Vec1<int>
Examples
There are a couple of generated example collections in examples/collections.go.
The go:generate command used can be found in examples/types.go.
This illustrates the core usage pattern:
//go:generate peds -vectors=IntVector<int> -pkg=my_collections -file=collections/my_collections_gen.go
// Create a new vector
v := my_collections.NewIntVector(1, 2, 3)
// Create a copy of v with the first element set to 55, v is left untouched.
v2 := v.Set(0, 55)
Godoc
Generic types
https://godoc.org/github.com/tobgu/peds/internal/generic_types
Generated examples
https://godoc.org/github.com/tobgu/peds/examples
Experiences
There's an experience report based on the implementation of this library.
Caveats
- Even though the data structures are immutable by most means it is not possible to use them as keys in hash maps for example. This is because they internally make use of slices, which are not comparable in Go.
Possible improvements
- Investigate implementing the Map as a CHAMP tree.
- Introspection of the contained types possible to refine the hash functions?
- Get rid of Python dependency for developing peds (not needed to build or use peds).
Regenerate templates and run tests
make test
Want to contribute?
Great! Write an issue and let the discussions begin! Then file a PR!