Spreadsheet-like dataflow programming in TypeScript

Aug 06, 2021
Spreadsheet-like dataflow programming in TypeScript


The reactive library for the spreadsheet driven development


import { cell, formula, swap, deref } from '@snapview/sunrise' const inc = (a) => a + 1 // Source Cell with initial value 1 const x = cell<number>(1) // Formula Cell created by incrementing the source cell const y = formula(inc, x) // Formula Cell without any value, but with side effect const printCell = formula(console.log, y) // Swapping the value of initial source cell swap(inc, x) deref(x) // 2 deref(y) // 3, this value is already printed to console because of printCell


Sunrise provides a spreadsheet-like computing environment consisting
of source cells and formula cells and introduces the Cell
interface to represent both

All Cells

  • Contain values
  • Implement the Dereferencable interface and their value can be extracted via the deref function
  • Implement the Destroyable interface and can be destroyed via the destroy function
  • Implement the Subscribable interface and can be subscribed via the subscribe function
    and unsubscribed via the unsubscribe function

Source Cells

The source cell is just a container including a value of arbitrary type. To construct
the source cell the cell function should be used

const a = cell<number>(1) // a cell of number const b = cell<string>('hello') // a cell of string const c = cell({ x: 1, y: 2 }) // an object cell const d = cell<string | undefined>(undefined) // a cell that can be either string or undefined

To receive the current value of a cell the deref function is used. Unlike many other
reactive libraries in Sunrise this is considered to be a totally valid operation.
A cell is not a stream or any other magic thing, it's just a box with a value inside

deref(a) // 1 deref(b) // 'hello' deref(c) // { x: 1, y: 2 } deref(d) // undefined

There are two ways to change a value inside a cell reset and swap. reset just
sets a new value to and swap accepts a function from old value to new value, applies
it and swap the cell to the new value

const a = cell<number>(1) reset(2, a) deref(a) // 2 swap((x) => x + 1) deref(a) // 3

reset and swap are async operations, the new value will be set not immediately, but
they implement the Software Transaction Memory
and they are always consistent.

In case you don't need a cell anymore, the cell can be destroyed with the destroy function.
Be careful because destroying the cell will also destroy all the dependent cells as well.
After the destruction, any operation on a cell is illegal, and throw the OperationOnDestroyedCellError

const x = cell<number>(1) const y = formula((a) => a + 1, x) destroy(x) // both x and y are destroyed now

Formula Cells

A formula cell is a sort of materialized view of a function. You can look at it as a cell with a formula inside in some table processor program. To create a formula cell
you need a formula (function) and an arbitrary number of source cells as an input

const a = cell<number>(1) const b = formula((x) => x + 1, a) // now b is always an increment of a deref(b) // 2 reset(5, a) deref(b) // 6

You can also use simple values as input to formula instead of cells. This might be
quite handy when you don't know if the input is a cell or just a value

const x = cell<number>(1) const y = cell<number>(2) const z: number = 3 const sum = formula((a, b, c) => a + b + c, x, y, z) deref(sum) // 6 reset(5, x) deref(sum) // 10

Predefined formula cells

There are quite some formula cells predefined for faster cell generations

Object's field

To extract one field from an object you can use the field function

const x = cell({ a: 1, b: 2 }) const fld = field('a', x) deref(fld) // 1 swap((x) => ({ ...x, a: 2 }), x) deref(fld) // 2
An element of an array

To extract an element from an array by index you can use the byIndex function.
The type of the result is Cell<T | undefined> because it's not guaranteed
that the element is presented

const x = cell(['a', 'b', 'c']) const el = byIndex(1, x) deref(el) // 'b' swap((x) => ['z', ...x], x) deref(el) // 'a'
Convert to boolean

To check that an element is truthy you can use the toBool function.

const x = cell(1) deref(toBool(x)) // true const y = cell<string | undefined>(undefined) deref(toBool(y)) // false
const x = cell<boolean>(true) deref(not(x)) // false const y = cell(1) deref(not(y)) // false

In some cases, it's useful to have both the old cell's value and the new one.
For this purpose, history can be used. It serves a tuple with the old and new
values inside. Be aware, initially, the old value is undefined

const x = cell<number>(1) const hist = history(x) deref(hist) // [1, undefined] reset(2, x) deref(hist) // [2, 1]