Type classes

export interface Indexable<F> extends Lookup<F> {
  index: <A>(fa: HKT<F, A>) => (key: Key<F>) => A
}

export interface Indexable1<F extends Keyed1 & URIS> extends Lookup1<F> {
  index: <A>(fa: Kind<F, A>) => (key: KeyOf1<F>) => A
}

export interface Indexable2<F extends Keyed2 & URIS2> extends Lookup2<F> {
  index: <E, A>(fa: Kind2<F, E, A>) => (key: KeyOf2<F, E>) => A
}

export interface Indexable2C<F extends Keyed2 & URIS2, E> extends Lookup2C<F, E> {
  index: <A>(fa: Kind2<F, E, A>) => (key: KeyOf2<F, E>) => A
}

export interface Indexable3<F extends Keyed3 & URIS3> extends Lookup3<F> {
  index: <R, E, A>(fa: Kind3<F, R, E, A>) => (key: KeyOf3<F, R, E>) => A
}

export interface Indexable3C<F extends Keyed3 & URIS3, E> extends Lookup3C<F, E> {
  index: <R, A>(fa: Kind3<F, R, E, A>) => (key: KeyOf3<F, R, E>) => A
}

export interface Indexable4<F extends Keyed4 & URIS4> extends Lookup4<F> {
  index: <S, R, E, A>(fa: Kind4<F, S, R, E, A>) => (key: KeyOf4<F, S, R, E>) => A
}