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Type-safe, zero-allocation sets for Go
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README.md

Set GoDoc Go Report Card Build Status

Package set is a type-safe, zero-allocation port of the excellent package fatih/set. It contains sets for most of the basic types and you can generate sets for your own types with ease.

Example

Example code using the generated string set:

import "github.com/scylladb/go-set/strset"

s1 := strset.New("entry 1", "entry 2")
s2 := strset.New("entry 2", "entry 3")
s3 := strset.Intersection(s1, s2)
// s3 now contains only "entry 2"

The library exposes a number of top level factory functions that can be used to create a specific instances of the set type you want to use. For example to create a set to store int you could do like this:

import "github.com/scylladb/go-set"

s := set.NewIntSet()
// use the set...

Usage

In every subpackage Set is the main set structure that holds all the data and methods used to working with the set.

func Difference

func Difference(set1 *Set, sets ...*Set) *Set

Difference returns a new set which contains items which are in in the first set but not in the others.

func Intersection

func Intersection(sets ...*Set) *Set

Intersection returns a new set which contains items that only exist in all given sets.

func New

func New(ts ...T) *Set

New creates and initializes a new Set.

func NewWithSize

func NewWithSize(size int) *Set

NewWithSize creates a new Set and gives make map a size hint.

func SymmetricDifference

func SymmetricDifference(s *Set, t *Set) *Set

SymmetricDifference returns a new set which s is the difference of items which are in one of either, but not in both.

func Union

func Union(sets ...*Set) *Set

Union is the merger of multiple sets. It returns a new set with all the elements present in all the sets that are passed.

func (*Set) Add

func (s *Set) Add(items ...T)

Add includes the specified items (one or more) to the Set. The underlying Set s is modified. If passed nothing it silently returns.

func (*Set) Clear

func (s *Set) Clear()

Clear removes all items from the Set.

func (*Set) Copy

func (s *Set) Copy() *Set

Copy returns a new Set with a copy of s.

func (*Set) Each

func (s *Set) Each(f func(item T) bool)

Each traverses the items in the Set, calling the provided function for each Set member. Traversal will continue until all items in the Set have been visited, or if the closure returns false.

func (*Set) Has

func (s *Set) Has(items ...T) bool

Has looks for the existence of items passed. It returns false if nothing is passed. For multiple items it returns true only if all of the items exist.

func (*Set) IsEmpty

func (s *Set) IsEmpty() bool

IsEmpty reports whether the Set is empty.

func (*Set) IsEqual

func (s *Set) IsEqual(t *Set) bool

IsEqual test whether s and t are the same in size and have the same items.

func (*Set) IsSubset

func (s *Set) IsSubset(t *Set) bool

IsSubset tests whether t is a subset of s.

func (*Set) IsSuperset

func (s *Set) IsSuperset(t *Set) bool

IsSuperset tests whether t is a superset of s.

func (*Set) List

func (s *Set) List() []T

List returns a slice of all items. There is also StringSlice() and IntSlice() methods for returning slices of type string or int.

func (*Set) Merge

func (s *Set) Merge(t *Set)

Merge is like Union, however it modifies the current Set it's applied on with the given t Set.

func (*Set) Pop

func (s *Set) Pop() T

Pop deletes and returns an item from the Set. The underlying Set s is modified. If Set is empty, the zero value is returned.

func (*Set) Pop2

func (s *Set) Pop2() (T, bool)

Pop2 tries to delete and return an item from the Set. The underlying Set s is modified. The second value is a bool that is true if the item existed in the set, and false if not. If Set is empty, the zero value and false are returned.

func (*Set) Remove

func (s *Set) Remove(items ...T)

Remove deletes the specified items from the Set. The underlying Set s is modified. If passed nothing it silently returns.

func (*Set) Separate

func (s *Set) Separate(t *Set)

Separate removes the Set items containing in t from Set s. Please aware that it's not the opposite of Merge.

func (*Set) Size

func (s *Set) Size() int

Size returns the number of items in a Set.

func (*Set) String

func (s *Set) String() string

String returns a string representation of s

Performance

The improvement in performance by using concrete types over interface{} is notable. Below you will find benchmark results comparing type-safe sets to fatih/set counterparts for string, int64, int32, float64 and float32 on a local machine, Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz.

pkg: github.com/scylladb/go-set/strset
BenchmarkTypeSafeSetHasNonExisting-4            200000000                7.02 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasNonExisting-4           20000000                60.0 ns/op            32 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExisting-4               200000000                9.02 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExisting-4              20000000                97.0 ns/op            32 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExistingMany-4           100000000               16.8 ns/op             0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExistingMany-4          30000000               106 ns/op              32 B/op          2 allocs/op
BenchmarkTypeSafeSetAdd-4                        3000000               469 ns/op              58 B/op          0 allocs/op
BenchmarkInterfaceSetAdd-4                       2000000               909 ns/op             117 B/op          2 allocs/op

pkg: github.com/scylladb/go-set/i64set
BenchmarkTypeSafeSetHasNonExisting-4            300000000                5.51 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasNonExisting-4           30000000                49.4 ns/op            24 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExisting-4               200000000                7.53 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExisting-4              20000000                68.5 ns/op            24 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExistingMany-4           100000000               11.0 ns/op             0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExistingMany-4          20000000                74.5 ns/op            24 B/op          2 allocs/op
BenchmarkTypeSafeSetAdd-4                       10000000               225 ns/op              40 B/op          0 allocs/op
BenchmarkInterfaceSetAdd-4                       3000000               403 ns/op              82 B/op          2 allocs/op

pkg: github.com/scylladb/go-set/i32set
BenchmarkTypeSafeSetHasNonExisting-4            300000000                5.61 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasNonExisting-4           30000000                48.8 ns/op            20 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExisting-4               200000000                7.07 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExisting-4              20000000                69.3 ns/op            20 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExistingMany-4           100000000               11.7 ns/op             0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExistingMany-4          20000000                71.1 ns/op            20 B/op          2 allocs/op
BenchmarkTypeSafeSetAdd-4                       10000000               206 ns/op              25 B/op          0 allocs/op
BenchmarkInterfaceSetAdd-4                       3000000               394 ns/op              78 B/op          2 allocs/op

pkg: github.com/scylladb/go-set/f64set
BenchmarkTypeSafeSetHasNonExisting-4            300000000                5.82 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasNonExisting-4           30000000                49.8 ns/op            24 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExisting-4               50000000                26.8 ns/op             0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExisting-4              20000000                77.6 ns/op            24 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExistingMany-4           50000000                27.6 ns/op             0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExistingMany-4          20000000                82.3 ns/op            24 B/op          2 allocs/op
BenchmarkTypeSafeSetAdd-4                       10000000               270 ns/op              40 B/op          0 allocs/op
BenchmarkInterfaceSetAdd-4                       3000000               428 ns/op              82 B/op          2 allocs/op

pkg: github.com/scylladb/go-set/f32set
BenchmarkTypeSafeSetHasNonExisting-4            300000000                5.78 ns/op            0 B/op          0 allocs/op
BenchmarkInterfaceSetHasNonExisting-4           30000000                49.3 ns/op            20 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExisting-4               50000000                24.9 ns/op             0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExisting-4              20000000                78.6 ns/op            20 B/op          2 allocs/op
BenchmarkTypeSafeSetHasExistingMany-4           50000000                25.1 ns/op             0 B/op          0 allocs/op
BenchmarkInterfaceSetHasExistingMany-4          20000000                81.1 ns/op            20 B/op          2 allocs/op
BenchmarkTypeSafeSetAdd-4                       10000000               246 ns/op              24 B/op          0 allocs/op
BenchmarkInterfaceSetAdd-4                       3000000               408 ns/op              78 B/op          2 allocs/op

Code generation

For code generation we use Google go_generics tool that we forked to provide bazel-free installation, to install run:

go get -u github.com/mmatczuk/go_generics/cmd/go_generics

Once you have go_generics installed properly you can regenerate the code using go generate in the top level directory.

Your custom types

If you have types that you would like to use but the are not amenable for inclusion in this library you can simply generate code on your own and put it in your package.

For example, to generate a set for SomeType in package sometypeset call:

./gen_set.sh SomeType sometypeset

this would generate a new directory sometypeset in current working directory.

If you think your addition belongs here we are open to accept pull requests.

License

Copyright (C) 2018 ScyllaDB

This project is distributed under the Apache 2.0 license. See the LICENSE file for details. It contains software from:

GitHub star is always appreciated!

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