Function chain_

packages/effect-app/src/Set.ts:205–220

(
  E: Equivalence.Equivalence<B>
)

 * Map + Flatten
 */
export function chain_<B>(
  E: Equivalence.Equivalence<B>
): <A>(set: Set<A>, f: (x: A) => Set<B>) => Set<B> {
  const elemE = elem_(E)
  return (set, f) => {
    const r = new Set<B>()
    set.forEach((e) => {
      f(e).forEach((e) => {
        if (!elemE(r, e)) {
          r.add(e)
        }
      })
    })
    return r
  }
}

/**
 * `true` if and only if every element in the first set is an element of the second set