Function fromUndefinedOr

repos/effect/packages/effect/src/Option.ts:860–862

(
  a: A
)

 * **Example** (Lifting a parser)
 *
 * ```ts import.meta.vitest
 * import { Option } from "effect"
 *
 * const parse = (s: string): number | undefined => {
 *   const n = parseFloat(s)
 *   return isNaN(n) ? undefined : n