This reference presents the syntax of Azoth using two grammars. The lexical grammar defines how characters combine to define tokens. The syntactic grammar defines how the tokens resulting from the lexical grammar are combined to form Azoth programs.
The grammars in this reference use a variant of BNF. They are not formal and may be ambiguous or have a structure which is not supported by certain parsing algorithms. Ambiguity in the grammar may be resolved by additional restrictions stated alongside the grammar. The notation used is summarized in the table below. Lexical grammars operate over unicode scalar values, thus whitespace cannot occur between symbols. In lexical grammars, the longest match is taken. Syntactic grammars operate over tokens, and symbols may be separated by whitespace.
| Syntax | Meaning |
|---|---|
| name | A nonterminal |
name : expression ; |
A derivation rule for the nonterminal name |
name <(parameter (= value)?){,, 1, *} > |
A parametrized derivation rule for the nonterminal name |
expression | expression |
Unordered choice |
expression* |
Expression repeated zero or more times |
expression+ |
Expression repeated one or more times |
expression? |
Expression is optional |
(expression) |
Expression grouping, provides order of operations |
expression{(separator ,)? n} |
Repeat expression n times, separated by separator if provided |
expression{(separator ,)? n, m} |
Repeat expression between n and m times, separated by separator if provided |
expression{(separator ,)? n, *} |
Repeat expression n or more times, separated by separator if provided |
expression - expression |
Match the first expression except if it matches the second expression |
\u(hex digits) |
A single unicode code point |
[character class] |
A regular expression style character class (^ negates a class, \ escapes, and - matches a range) |
\p{unicode class} |
Match any single character in the given Unicode class |
"literal" |
Matches a literal string (no escape sequences are supported) |
?description? |
Matches a string according to the description |
// comment newline |
A line comment |
/* comment */ |
A multi-line comment |