ring

Documentation

Overview

Package ring implements operations on circular lists.

Index

• type Ring
  • func New(n int) *Ring
  • func (r *Ring) Do(f func(interface{}))
  • func (r *Ring) Len() int
  • func (r *Ring) Link(s *Ring) *Ring
  • func (r *Ring) Move(n int) *Ring
  • func (r *Ring) Next() *Ring
  • func (r *Ring) Prev() *Ring
  • func (r *Ring) Unlink(n int) *Ring

Examples

• Ring.Do
• Ring.Len
• Ring.Link
• Ring.Move
• Ring.Next
• Ring.Prev
• Ring.Unlink

Types

type Ring

type Ring struct {
	Value interface{} // for use by client; untouched by this library
	// contains filtered or unexported fields
}

A Ring is an element of a circular list, or ring. Rings do not have a beginning or end; a pointer to any ring element serves as reference to the entire ring. Empty rings are represented as nil Ring pointers. The zero value for a Ring is a one-element ring with a nil Value.

func New

func New(n int) *Ring

New creates a ring of n elements.

func (*Ring) Do

func (r *Ring) Do(f func(interface{}))

Do calls function f on each element of the ring, in forward order. The behavior of Do is undefined if f changes *r.

Example

package main

import (
	"container/ring"
	"fmt"
)

func main() {
	// Create a new ring of size 5
	r := ring.New(5)

	// Get the length of the ring
	n := r.Len()

	// Initialize the ring with some integer values
	for i := 0; i < n; i++ {
		r.Value = i
		r = r.Next()
	}

	// Iterate through the ring and print its contents
	r.Do(func(p interface{}) {
		fmt.Println(p.(int))
	})

}

Output:

0
1
2
3
4

func (*Ring) Len

func (r *Ring) Len() int

Len computes the number of elements in ring r. It executes in time proportional to the number of elements.

Example

package main

import (
	"container/ring"
	"fmt"
)

func main() {
	// Create a new ring of size 4
	r := ring.New(4)

	// Print out its length
	fmt.Println(r.Len())

}

Output:

4

func (*Ring) Link

func (r *Ring) Link(s *Ring) *Ring

Link connects ring r with ring s such that r.Next() becomes s and returns the original value for r.Next(). r must not be empty.

If r and s point to the same ring, linking them removes the elements between r and s from the ring. The removed elements form a subring and the result is a reference to that subring (if no elements were removed, the result is still the original value for r.Next(), and not nil).

If r and s point to different rings, linking them creates a single ring with the elements of s inserted after r. The result points to the element following the last element of s after insertion.

Example

package main

import (
	"container/ring"
	"fmt"
)

func main() {
	// Create two rings, r and s, of size 2
	r := ring.New(2)
	s := ring.New(2)

	// Get the length of the ring
	lr := r.Len()
	ls := s.Len()

	// Initialize r with 0s
	for i := 0; i < lr; i++ {
		r.Value = 0
		r = r.Next()
	}

	// Initialize s with 1s
	for j := 0; j < ls; j++ {
		s.Value = 1
		s = s.Next()
	}

	// Link ring r and ring s
	rs := r.Link(s)

	// Iterate through the combined ring and print its contents
	rs.Do(func(p interface{}) {
		fmt.Println(p.(int))
	})

}

Output:

0
0
1
1

func (*Ring) Move

func (r *Ring) Move(n int) *Ring

Move moves n % r.Len() elements backward (n < 0) or forward (n >= 0) in the ring and returns that ring element. r must not be empty.

Example

package main

import (
	"container/ring"
	"fmt"
)

func main() {
	// Create a new ring of size 5
	r := ring.New(5)

	// Get the length of the ring
	n := r.Len()

	// Initialize the ring with some integer values
	for i := 0; i < n; i++ {
		r.Value = i
		r = r.Next()
	}

	// Move the pointer forward by three steps
	r = r.Move(3)

	// Iterate through the ring and print its contents
	r.Do(func(p interface{}) {
		fmt.Println(p.(int))
	})

}

Output:

3
4
0
1
2

func (*Ring) Next

func (r *Ring) Next() *Ring

Next returns the next ring element. r must not be empty.

Example

package main

import (
	"container/ring"
	"fmt"
)

func main() {
	// Create a new ring of size 5
	r := ring.New(5)

	// Get the length of the ring
	n := r.Len()

	// Initialize the ring with some integer values
	for i := 0; i < n; i++ {
		r.Value = i
		r = r.Next()
	}

	// Iterate through the ring and print its contents
	for j := 0; j < n; j++ {
		fmt.Println(r.Value)
		r = r.Next()
	}

}

Output:

0
1
2
3
4

func (*Ring) Prev

func (r *Ring) Prev() *Ring

Prev returns the previous ring element. r must not be empty.

Example

package main

import (
	"container/ring"
	"fmt"
)

func main() {
	// Create a new ring of size 5
	r := ring.New(5)

	// Get the length of the ring
	n := r.Len()

	// Initialize the ring with some integer values
	for i := 0; i < n; i++ {
		r.Value = i
		r = r.Next()
	}

	// Iterate through the ring backwards and print its contents
	for j := 0; j < n; j++ {
		r = r.Prev()
		fmt.Println(r.Value)
	}

}

Output:

4
3
2
1
0

func (*Ring) Unlink

func (r *Ring) Unlink(n int) *Ring

Unlink removes n % r.Len() elements from the ring r, starting at r.Next(). If n % r.Len() == 0, r remains unchanged. The result is the removed subring. r must not be empty.

Example

package main

import (
	"container/ring"
	"fmt"
)

func main() {
	// Create a new ring of size 6
	r := ring.New(6)

	// Get the length of the ring
	n := r.Len()

	// Initialize the ring with some integer values
	for i := 0; i < n; i++ {
		r.Value = i
		r = r.Next()
	}

	// Unlink three elements from r, starting from r.Next()
	r.Unlink(3)

	// Iterate through the remaining ring and print its contents
	r.Do(func(p interface{}) {
		fmt.Println(p.(int))
	})

}

Output:

0
4
5