Function changeMap

packages/effect/src/SchemaAST.ts:2743–2755

(as: ReadonlyArray<A>, f: (a: A) => A)

): Arr.NonEmptyReadonlyArray<A>
function changeMap<A>(as: ReadonlyArray<A>, f: (a: A) => A): ReadonlyArray<A>
function changeMap<A>(as: ReadonlyArray<A>, f: (a: A) => A): ReadonlyArray<A> {
  let changed = false
  const out = Arr.allocate(as.length) as Array<A>
  for (let i = 0; i < as.length; i++) {
    const a = as[i]
    const fa = f(a)
    if (fa !== a) {
      changed = true
    }
    out[i] = fa
  }
  return changed ? out : as
}

/**
 * Returns the from part of a transformation if it exists