optional

The Optional of the family: a value that is present (some) or absent (none). It replaces null, undefined and exceptions in a total evaluation.

import { fromNullable, getOr, map, none, some, type Optional } from "@mark1russell7/optional";

const width: Optional<number> = some(4);
getOr(map(width, (w) => w * 2), 0); // 8
getOr(fromNullable(undefined), 0);  // 0

Users

Project	Use
render	`@render/optional` gives the exports of this package.
Vex	The type `Optional` of `@mark1russell7/vex` is the type of this package.
Graph	Graph uses a sentinel form: a value or the symbol `NotFound`. `fromSentinel` and `toSentinel` change between the two forms.

API

Export	What it does
`Optional<T>`, `Some<T>`, `None`	The types: `{ tag: "some", value }` or `{ tag: "none" }`
`some(value)`, `none`	The two kinds of value. `none` is one frozen object.
`isSome(o)`, `isNone(o)`	The type guards
`map(o, f)`, `flatMap(o, f)`	`f` applies to a present value. An absent value stays absent. The tests check the functor laws and the monad laws.
`unwrap(o)`, `getOr(o, fallback)`	The present value, or `undefined`, or the fallback
`fromNullable(value)`	`none` for `null` and `undefined`, else `some(value)`
`fromSentinel(value, sentinel)`, `toSentinel(o, sentinel)`	The change between this form and a sentinel form

Commands

pnpm install
pnpm check    # the type check, the tests and the writing rules
pnpm build    # dist/: commit it after a change, because a github: dependency does not build the package

Writing style

The prose of this repository follows ASD-STE100 Simplified Technical English (STE). STE is a style target. ASD does not certify this repository.

License

MIT