powerfp

Installation

npm install powerfp

Features

• implementation of useful algebraic data types: Option, Result, ResultS, Tree, List
• utility functions used for function composition: compose, pipe, curry
• infrastructure for the implementation of functors, monads and applicative functors in TypeScript
• functors, monads and applicative functors implementation for algebraic data type (Option, Result, ResultS, Tree, List) and other commonly used types (Array, Promise, Iterable, Observable, IO)
• do Haskell notation using ES6 generators
• code generators for algebraic data types and functors, monads and applicative functors
• utility functions like memoize and functions extracted from types like string, Regex (useful with function composition)
• SumType type inferring ADT type from the constructor functions
• matchValue predicate function matching single value against specified pattern (primitive values, object, array)
• match function providing "pattern matching" functionality
• toOption converting value of type T|null|undefined into Option<T>

Sample code

import { Option, none, some } from "powerfp";

function tryParseNumber(text: string): Option<number> {
  const n = Number(text);
  return Number.isNaN(n) ? none : some(n);
}


// ** powerfp**
type Option<T> =        
  | { type: "some", value: T }
  | { type: "none" };   

import { matchUnion, isUnion } from "powerfp";

function format(n: Option<number>) : string{
    return matchUnion(n, {
        some: ({ value }) => `${Math.round(value)} zl`,
        none: () => "0 zl"        
    });
}

const o: Option<number> = ...;
console.log(isUnion(o, "some") ? o.value : "");

more detailed documentation coming soon ..