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import { IOptional, Mapper, Optional } from '@emprespresso/pengueno';
export interface ICons<T> extends Iterable<T> {
readonly value: T;
readonly next: IOptional<ICons<T>>;
readonly replace: Mapper<T, ICons<T>>;
readonly before: Mapper<IOptional<ICons<T>>, ICons<T>>;
}
export class Cons<T> implements ICons<T> {
constructor(
public readonly value: T,
public readonly next: IOptional<ICons<T>> = Optional.none(),
) {}
public before(head: IOptional<ICons<T>>): ICons<T> {
return new Cons<T>(this.value, head);
}
public replace(_value: T): ICons<T> {
return new Cons<T>(_value, this.next);
}
*[Symbol.iterator]() {
for (let cur = Optional.some<ICons<T>>(this); cur.present(); cur = cur.flatMap((cur) => cur.next)) {
yield cur.get().value;
}
}
static addOnto<T>(items: Iterable<T>, tail: IOptional<ICons<T>>): IOptional<ICons<T>> {
return Array.from(items)
.reverse()
.reduce((cons, value) => Optional.from<ICons<T>>(new Cons<T>(value, cons)), tail);
}
static from<T>(items: Iterable<T>): IOptional<ICons<T>> {
return Cons.addOnto(items, Optional.none());
}
}
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