Select syntax
=============

Goals:
- It should be obvious what happens, even if you don't know SLUL,
  and preferably also if you don't know specific other languages
  such as C, C++, Java, Javascript, Python, Perl, etc.

Syntax 1
--------

    color = select is_open (true -> .green, false -> .red)

    is_operator = select token (
        .plus -> true,
        .minus -> true,
        .number -> false)