Duplicate an endpoint config, then apply a partial timeout update to it.

  copied :=: original
  target :~: patch

defines module qa.operators.copyvsmergereplace

  defines class

    Endpoint
      url <- String()
      timeout <- Integer()
      retries <- Integer()

      Endpoint()
        ->
          url as String
          timeout as Integer
          retries as Integer
        this.url :=: url
        this.timeout :=: timeout
        this.retries :=: retries

      //Constructor for partial updates — only timeout
      Endpoint()
        -> timeout as Integer
        this.timeout :=: timeout

      operator :~:
        -> from as Endpoint
        if from.url?
          url :=: from.url
        if from.timeout?
          timeout :=: from.timeout
        if from.retries?
          retries :=: from.retries

      default operator ?
      default operator $
      default operator :=:

  defines program

    CopyVsMergeReplaceDemo()
      stdout <- Stdout()

      original <- Endpoint("https://api.example.com", 30, 3)

      // :=: COPY — exact duplicate of all fields
      copied <- Endpoint()
      copied :=: original
      stdout.println(`Copy: ${copied}`)

      // :~: MERGE — only the set timeout field is applied
      patch <- Endpoint(60)
      target <- Endpoint("https://old.example.com", 10, 1)
      stdout.println(`Before merge: ${target}`)
      target :~: patch
      stdout.println(`After merge: ${target}`)