import Base{Code}

// From Base
App3[left, center, right].

Prgm[statement].
Print[text].

// From Base
App3[left: #String[], center: #String[], right: #String[]]:
  #App3[a: left<App3, b: center<App3, c: right<App3]

Prgm[statement: Code[lang: "C", content: #String[]]]: Code[
  lang: "C"
  content: App3[
    left: "int main(string[] args) {\n  "
    center: statement<Prgm>content<Code
    right: "\n}"
  ]
]
Print[text: #String[]]: Code[
  lang: "C"
  content: App3[left: "println(\"", center: text<Print, right: "\");"]
]

Prgm[statement: Print[text: "Hello world"]]?