history

@algorithm.ts/history

A simple data structure to manage history through circular stack.

Install

• npm

  npm install --save @algorithm.ts/history

• yarn

  yarn add @algorithm.ts/history

Usage

History

History is a fixed size stack structure, the main purpose of its design is to reuse space as much as possible on the basis of ordinary historys. Historys usually need to specify a capacity, if the number of elements in the history exceeds the capacity, only the most recent capacity elements are preserved in the history. Other operations are the same as ordinary historys.

• IHistory: History implements the IHistory interface.

  Signature	Description
  readonly capacity: number	The capacity of the history, which also means the maximum elements of the history.
  readonly size: number	The count of the elements in the history.
  readonly name: string	The name of the history.
  readonly equals: IEquals	Used to check if two element in the history are same.
  backward(step?: number): [element: T | undefined, isBot: boolean]	Backward step steps and return the present element of the history.
  clear(): void	Clear the history.
  count(filter: (element: T, index: number) => boolean): number	Count the elements in the history which matched the filter.
  fork(name: string): IHistory<T>	Create a new history from the current one.
  forward(step?: number): [element: T | undefined, isTop: boolean]	Forward step steps and return the present from the history.
  go(index?: number): T | undefined	Set the present index to the given index and return the elements at the index of the history.
  isBot(): boolean	Check if the present index is at the bottom of the history.
  isTop(): boolean	Check if the present index is at the top of the history.
  present(): [element: T | undefined, index: number]	Return the present element and present index of the history.
  push(element: T): this	Push the element to the history.
  rearrange(filter: (element: T, index: number) => boolean): void	Rearrange the history and only keep the elements matched the given filter.
  updateTop(element: T): void	Change the top element of the history.

• IHistoryProps

  export interface IHistoryProps<T> {
    /**
    * The history name.
    */
    readonly name: string
    /**
    * Initial capacity of the circular history.
    */
    readonly capacity: number
    /**
    * Used to check if two element in the history are same.
    */
    readonly equals?: IEquals<T>
  }

Example

• Basic -- CircularHistory

  import { History } from '@algorithm.ts/history'
  
  const history = new History<{ name: string }>({ name: 'profile', capacity: 100 })
  
  // Append a element to the end of the history.
  history.push({ name: 'alice' }) // => 0
  history.push({ name: 'bob' }) // => 1
  history.size          // => 2
  
  // Get the front element of the history.
  history.present()     // => [{ name: 'bob' }, 1]
  history.backward()    // => [{ name: 'alice' }, 0]
  history.backward()    // => [{ name: 'alice' }, 0]
  history.forward()     // => [{ name: 'bob' }, 1]
  history.forward()     // => [{ name: 'bob' }, 1]

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