31 lines
606 B
TypeScript
31 lines
606 B
TypeScript
export interface Maybe<T> {
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isJust(): this is Just<T>;
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map<S>(f: (x: T) => S): Maybe<S>;
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getOrElse(x: T): T;
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}
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export type Just<T> = Maybe<T> & {
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get(): T
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};
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export function just<T>(value: T): Just<T> {
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return {
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isJust: () => true,
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getOrElse: (_: T) => value,
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map: <S>(f: (x: T) => S) => just(f(value)),
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get: () => value
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};
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}
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export function nothing<T>(): Maybe<T> {
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return {
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isJust: () => false,
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getOrElse: (value: T) => value,
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map: <S>(_: (x: T) => S) => nothing<S>()
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};
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}
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export function fromNullable<T>(value: T): Maybe<T> {
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return value == null ? nothing() : just(value);
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}
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