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stl4go -- STL for Golang

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This library contains generic containers and algorithms, it is designed to be STL for Golang.

License Apache 2.0 Golang Build Status Coverage Status GoReport Go Reference

This library depends on go generics, which is introduced in 1.18+.

import "github.com/chen3feng/stl4go"

Package stl4go is a generic container and algo rithm library for go.

Introduce

This library is a general container and algorithm library that attempts to learn from the C++ STL implementation after Go 1.18 began to support generics. (Personally I's totally unacceptable for me use to languages without generics, so I didn't try it until go 1.18).

The code quality of this library is quite high and follows the latest best practices in the industry. Test coverage is close💯%, ✅，CI, and gosec check are both set up, got GoReport score。

Features

As we all know, C++'s STL includes containers, algorithms, and iterators relate the two.

Due to language limitations, it is impossible and unnecessary to completely imitate the interface of C++ STL in Go, so C++ users may feel familiar, and sometimes (maybe) feel more convenient.

Containers

Currently implemented containers are:

  • BuiltinSet provided a set funtionality based on Go's own map
  • Vector is a thin encapsulation based on slice. It provides functions such as insertion and deletion in the middle, range deletion, etc., and is still compatible with slices.
  • DList is a doubly linked list.
  • SkipList is an ordered associative container that fills the gap where Go map only supports unordered. This is currently the fastest skip list I tested in GitHub, see skiplist-survey for performance comparison
  • Stack, is a FILO container based on Slice implementation
  • Queue is a bidirectional FIFO queue, implemented based on linked list.
  • PriorityQuque is a priority queue based on heap. Much easier to use and faster than container/heap.

Different containers support different methods. The following are the methods supported by all containers:

  • IsEmpty() bool Returns whether the container is empty
  • Len() int returns the number of elements in the container
  • Clear() to clear the container

Iterators

Vector, DList and SkipList support iterators.

// Iterator is the interface for container's iterator.
type Iterator[T any] interface {
	IsNotEnd() bool // Whether it is point to the end of the range.
	MoveToNext()    // Let it point to the next element.
	Value() T       // Return the value of current element.
}

// MutableIterator is the interface for container's mutable iterator.
type MutableIterator[T any] interface {
	Iterator[T]
	Pointer() *T // Return the pointer to the value of current element.
}
l := stl4go.NewDListOf(Range(1, 10000)...)
sum := 0
for i := 0; i < b.N; i++ {
    for it := l.Iterate(); it.IsNotEnd(); it.MoveToNext() {
        sum += it.Value()
    }
}

The iterator of SkipList is MutableMapIterator:

// MapIterator is the interface for map's iterator.
type MapIterator[K any, V any] interface {
	Iterator[V]
	Key() K // The key of the element
}

// MutableMapIterator is the interface for map's mutable iterator.
type MutableMapIterator[K any, V any] interface {
	MutableIterator[V]
	Key() K // The key of the element
}

SkipList also supports range iteration:

sl := stl4go.NewSkipList[int, int]()
for i := 0; i < 1000; i++ {
    sl.Insert(i, 0)
}
it := sl.FindRange(120, 350)

Iterating over it only yields the keys between 120 and 349.

In many cases, it is more convenient to use the ForEach and ForEachIf methods provided by the container, and the performance is often better:

func TestSkipList_ForEach(t *testing.T) {
    sl := newSkipListN(100)
    a := []int{}
    sl.ForEach(func(k int, v int) {
        a = append(a, k)
    })
    expectEq(t, len(a), 100)
    expectTrue(t, IsSorted(a))
}

ForEachIf is used for scenarios that you want to end early during the iteration:

func Test_DList_ForEachIf(t *testing.T) {
   l := NewDListOf(1, 2, 3)
   c := 0
   l.ForEachIf(func(n int) bool {
       c = n
       return n != 2
   })
   expectEq(t, c, 2)
}

You can use ForEachMutable or ForEachMutable to modify the value of an element during the iteration:

func TestSkipList_ForEachMutable(t *testing.T) {
    sl := newSkipListN(100)
    sl.ForEachMutable(func(k int, v *int) {
        *v = -*v
    })
    for i := 0; i < sl.Len(); i++ {
        expectEq(t, *sl.Find(i), -i)
    }
}

Algorithms

Due to the limitations of language, most algorithms only support Slice. The functions name of the algorithms ends with If or Func, indicating that a custom comparison function can be passed.

Generate

  • Range returns a Slice of contains integers in the range of [begin, end)
  • Generate generates a sequence with the given function to fill the Slice

Compute

  • Sum Sum
  • SumAs sums and returns a result as another type (eg. use int64 to return the sum of []int32).
  • Average finds the average value.
  • AverageAs averages and returns the result as another type (eg. use float64 to return the sum of []int).
  • Count returns the number equivalent to the specified value
  • CountIf returns the number of elements for which the specified function returns true

Compare

  • Equal checks whether two sequences are equal
  • Compare compares two sequences and returns -1, 0, and 1 in lexicographical order, respectively indicating the relationship of 2 slices.

Lookup

  • Min, Max find the maximum and minimum
  • MinN, MaxN, MinMax return the maximum and minimum values in the slice
  • Find linearly finds the first specified value and returns its index
  • FindIf linearly finds the first value that make specified function returns true and returns its index
  • AllOf, AnyOf, NoneOf return whether all, any, or none of the elements in the range can make the passed function return true accordingly.

Binary Search

See C++ STL.

  • BinarySearch
  • LowerBound
  • UpperBound

Sort

  • Sort sorting
  • DescSort descending sorting
  • StableSort stable sorting
  • DescStableSort descending stable sorting
  • IsSorted check whether the slice is sorted
  • IsDescSorted check whether the slice is sorted in descending order

heap

Heap provides basic min heap algorithms:

  • MakeMinHeap Convert a slice to a min heap
  • IsMinHeap Check whether a slice is a min heap
  • PushMinHeap Pushes an element in to the heap
  • PopMinHeap Popups an element from the top of the heap
  • RemoveMinHeap Removes an element at index from the heap

and variants with custome comparasion function:

  • MakeHeapFunc
  • IsHeapFunc
  • PushHeapFunc
  • PopHeapFunc
  • RemoveHeapFunc

both of them are mush faster and easier to use than container/heap.

See detailed usage and benchmark report in the document of heap。

Interface Design and Naming

The design leart much from the C++ STL. The T here represents template. Yes, Go's generic is not template. but who made C++ so influential and STL so famous?

Many libraries are designed for small code repositories or split into multiple subpackages in one repository. For example:

import (
    "github.com/someone/awesomelib/skiplist"
    "github.com/someone/awesomelib/binarysearch"
)

func main() {
    sl := skiplist.New()
}

This way of writing seems elegant, but because everyone likes good names, import renaming has to be introduced in use in case of package name conflict, and different users have different renaming style, which increases the mental burden of code reading and writing.

I don't like this style, especially in a larger repository.

Therefore, this library is all under the stl4go package, and it is expected that it will not namesake in other people's libraries.

TODO

See Issue。

And add more detailed documents.

Go Doc

Click to view the generated doc.

Reference