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Options in TypeScript
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type None = { | |
flatMap<U>(f: (value: null) => Option<U>): None | |
getOrElse<U>(def: U): U | |
isEmpty(): true | |
map<U>(f: (value: null) => U): None | |
nonEmpty(): false | |
orElse<U>(alternative: Option<U>): Option<U> | |
} | |
type Some<T> = { | |
flatMap<U>(f: (value: T) => Some<U>): Some<U> | |
flatMap<U>(f: (value: T) => None): None | |
flatMap<U>(f: (value: T) => Option<U>): Option<U> | |
get(): T | |
getOrElse<U extends T>(def: U): T | U | |
isEmpty(): false | |
map(f: (value: T) => null): None | |
map<U>(f: (value: T) => U): Some<U> | |
map<U>(f: (value: T) => U): Option<U> | |
nonEmpty(): true | |
orElse<U extends T>(alternative: Option<U>): Option<T> | Option<U> | |
} | |
type Option<T> = Some<T> | None | |
let None: None = { | |
flatMap: <T>(_f: (value: never) => Option<T>) => None, | |
getOrElse: <T>(def: T) => def, | |
isEmpty: () => true, | |
map: <T>(_f: (value: never) => T) => None, | |
nonEmpty: () => false, | |
orElse: <U>(alternative: Option<U>): Option<U> => alternative | |
} | |
function Some<T>(value: T): Some<T> { | |
return { | |
flatMap: <U>(f: (value: T) => Option<U>) => f(value) as any, // TODO | |
get: () => value, | |
getOrElse: <U extends T>(def: U): T | U => value || def, | |
isEmpty: () => false, | |
map: <U>(f: (value: T) => U) => Option(f(value)) as any, // TODO | |
nonEmpty: () => true, | |
orElse: <U>(_alternative: Option<U>): Option<T> | Option<U> => Some(value) | |
} | |
} | |
function Option<T>(value: T): Some<T> | |
function Option<T>(value: null): None | |
function Option<T>(value: T | null) { | |
if (value === null) { | |
return None | |
} | |
return Some(value) | |
} | |
let y = Option(3) | |
.map(() => 4) | |
.flatMap(() => Option(5)) | |
.get() |
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