This is a small language.

  let source_code = r#"
      a = 100
      c = 20
      a + c
      fn add(v1,v2) {
          return v1 + v2
      }
      add(( add(1,2) + add(3,4) + add((3 + 2) * 3,1)),100)
      "#;

  let mut parser = Parser::new(source_code.into());
  let f = parser.parse_file().unwrap();
  // println!("{:?}",f);
  let i = Intepretor::new(f);
  let res = i.execute().unwrap();
  println!("{:?}", res);