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  • Record Types are combining several values into a structured value similar to a struct in C. An example record definition is given by
    .type Connection = [
      from : Place,
      to : Place

    defining values of ordered pairs of places. Each record type enumerates a list of nested, named fields and their types. Records may be nested as in

    .type Cargo = [
      flight : Connection,
      mass : weight

    as well as recursive, as in

    .type Path = [
      first : Connection,
      rest : Path

    Thus, a record may contain (directly or indirectly) fields of its own type. As a base case for recursive records, every record type contains the value nil, so we can represent lists as

    .type List = [
      head : number
      tail : List
    .decl A(x : List)

Union types involving records are currently not supported.