append method

@override IMap<K, V> append(IMap<K, V> m1, IMap<K, V> m2)

Implementation

@override IMap<K, V> append(IMap<K, V> m1, IMap<K, V> m2) =>
    m2.pairs().foldLeft(m1, (p, kv) =>
        m1.get(kv.value1).fold(() =>
            p.put(kv.value1, kv.value2),
            (m1v) => p.put(kv.value1, _vSemigroup.append(m1v, kv.value2))));