0.2 Notation

• The grammar is written in EBNF (appendix A): a? — optional, a* — zero or more, a+ — one or more, a | b — choice, "kw" — terminal.
• Code examples are informative; in case of a discrepancy with the text, the text prevails.
• T, U — arbitrary types; E — a union type of errors.
• The top level of a file contains declarations (items) only. The let and assert lines and the calls shown in examples outside a function (in §4.2, V.3 and others) are fragments: in a program such statements are located in the body of a function, main or test (D-8052, DIV-001, App. B).

Source: docs/spec/oxl-standard.en.md