howitworks-map-2.js

const map = (g, mapper, unmapper) => {
    return {
        generate(mrng) {
            return mapper(g.generate(mrng));
        },
        *shrink(value) {
            for (const shrunkValue of g.shrink(unmapper(value))) {
                yield mapper(shrunkValue);
            }
        }
    };
};