@jsoldi/hkt/dist/classes/unfold.js

Higher kinded types for typescript and a few utility monads.

import { functor } from "./functor.js";
import { maybe } from "../types/maybe.js";
import { pipe } from "../core/utils.js";
const is_unfold = Symbol('is_unfold');
/** Creates an `IUnfold` from an `IUnfoldBase`. */
export function unfold(base) {
    if (is_unfold in base)
        return base;
    return pipe(base, base => ({
        ...functor(base),
        ...base
    }), base => {
        const iterate = f => base.unfold(a => base.scalar.unit(maybe.map(f(a), a2 => [a, a2])));
        const forLoop = (init, pred, next) => iterate(a => pred(a) ? maybe.just(next(a)) : maybe.nothing)(init);
        const range = (start, end) => forLoop(start, t => t <= end, t => t + 1);
        const replicate = (n, a) => base.map(range(1, n), _ => a);
        return {
            ...{ [is_unfold]: true },
            iterate,
            forLoop,
            range,
            replicate,
            ...base,
        };
    });
}
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