Algebraic graphs in TypeScript
npm install alga-ts
alga-ts is a library for algebraic construction and manipulation of graphs in TypeScript. This is a TypeScript port of alga and alga-scala.
> See this Haskell Symposium paper and the corresponding talk for the motivation behind the library, the underlying theory and implementation details. There is also a Haskell eXchange talk, and a tutorial by Alexandre Moine.
N.B. Please note that this project is WIP, so use it at your own discretion.
The main library, alga-ts, is available at the NPM. As it uses fp-ts for higher-kinded types, be sure to install it as well:
``sh`
npm install --save alga-ts fp-ts
To begin using alga-ts, you first need to obtain an instance of it's API for the given Eq of your target data type. Consider the example:
`ts
import { getStructEq, eqNumber, eqString } from 'fp-ts/lib/Eq';
import { getInstanceFor } from 'alga-ts';
interface User {
name: string;
age: number;
}
const eqUser = getStructEq({
name: eqString,
age: eqNumber,
});
const G = getInstanceFor(eqUser);
`
Now G is a module containing all methods & constructors required to work with graphs of User:
`ts
const user1: User = { name: 'Alice', age: 32 };
const user2: User = { name: 'Bob', age: 41 };
const user3: User = { name: 'Charlie', age: 28 };
const graph1 = G.connect(
G.edge(user1, user2),
G.edge(user2, user3),
);
console.log(G.hasEdge(user1, user3, graph1)); // => true
`
Algbraic graphs happen to have type class instances for Monad (and, consequently, for Functor and Applicative) and Alternative. API instance, obtained via getInstanceFor, exposes methods from these type classes in a data-last form, so they could be used with pipe from fp-ts:
`ts
import { pipe } from 'fp-ts/lib/pipeable';
import { getInstanceFor } from 'alga-ts';
const GS = getInstanceFor(eqString);
...
const graph2 = pipe(
graph1,
G.map(u => u.name),
);
console.log(GS.hasEdge('Alice', 'Charlie', graph2)); // => true
``