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https://github.com/fantasyland/static-land
Specification for common algebraic structures in JavaScript based on Fantasy Land
https://github.com/fantasyland/static-land
adt algebra algebraic algebraic-data-types fantasy-land functional-programming functor monad monoid specification static-land
Last synced: 5 days ago
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Specification for common algebraic structures in JavaScript based on Fantasy Land
- Host: GitHub
- URL: https://github.com/fantasyland/static-land
- Owner: fantasyland
- License: mit
- Created: 2016-03-12T18:04:07.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2019-10-29T13:34:03.000Z (about 5 years ago)
- Last Synced: 2024-05-23T10:22:36.905Z (6 months ago)
- Topics: adt, algebra, algebraic, algebraic-data-types, fantasy-land, functional-programming, functor, monad, monoid, specification, static-land
- Language: JavaScript
- Homepage:
- Size: 117 KB
- Stars: 770
- Watchers: 23
- Forks: 40
- Open Issues: 11
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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- awesome-starred - fantasyland/static-land - Specification for common algebraic structures in JavaScript based on Fantasy Land (others)
README
# 
Static Land
This is a specification for common algebraic structures in JavaScript
based on [Fantasy Land](https://github.com/fantasyland/fantasy-land).
* [Specification](docs/spec.md)
### Difference from Fantasy Land
Fantasy Land uses methods to define interfaces that a type must implement in
order to support a particular Algebra. For example values of a type that
implements the Monoid algebra must have `fantasy-land/empty` and
`fantasy-land/concat` methods on them.
Static Land takes a different approach. Instead of methods, we use static
functions, that are grouped together in [modules](docs/spec.md#module).
For example, here is an Addition module that uses numbers as values and
satisfies the Monoid algebra requirements:
```js
const Addition = {
empty() {
return 0
},
concat(a, b) {
return a + b
},
}
```
#### Pros
- No name clashes. Since a module is just a collection of functions that don't
share any namespace we don't have problems with name clashes.
- We can implement many modules for one type, therefore we can have more than
one instance of the same Algebra for a single type. For example, we can
implement two Monoids for numbers: Addition and Multiplication.
- We can implement modules that work with built-in types as values (Number,
Boolean, Array, etc).
#### Cons
- We have to pass around modules when we write generic code. In Fantasy Land
most of generic code can be written using only methods, only if we need
methods like `of` or `empty` we might need to pass the type representative.
([This can be fixed!](https://github.com/rpominov/static-land/issues/45))
### How to add compatibility with Static Land to your library
Simply expose a [module](docs/spec.md#module) that works with types that your
library provides or with types defined in another library or with native types
like Array.
Modules don't have to be simple JavaScript objects; they can also be
constructors if desired. The only requirements are:
- this object contains some static methods from Static Land; and
- if it contains a method with one of the names that Static Land reserves, that
method must be the Static Land method (obey laws etc).
#### Example 1. Static Land module for Array
```js
const SArray = {
of(x) {
return [x]
},
map(fn, arr) {
return arr.map(fn)
},
chain(fn, arr) {
// ...
},
}
export {SArray}
```
#### Example 2. Static Land module as a Class
```js
class MyType {
constructor() {
// ...
}
someInstanceMethod() {
// ...
}
static someNonStaticLandStaticMethod() {
// ...
}
// Static Land methods
static of(x) {
// ...
}
static map(fn, value) {
// ...
}
}
export {MyType}
```
#### Example 3. Static Land module as ECMAScript modules
```js
// mytype.js
// Static Land methods
export function of(x) {
// ...
}
export function map(fn, value) {
// ...
}
```
Import as
```js
import * as MyType from "./mytype" // MyType is now a Static Land module
```
### Compatible libraries
We have a list in the wiki. Feel free to add your library there.
- [Compatible libraries](https://github.com/rpominov/static-land/wiki/Compatible-libraries)