expression -> | sequence // | apply | unary | binary | let | compound | control | field | index | identifier | primary grouping -> "(" expression ")" ; unary -> ( "-" | "!" ) expression ; binary -> expression operator expression ; operator -> | "==" | "!=" | "<" | "<=" | ">" | ">=" | "+" | "-" | "*" | "/" | "|>" | "<|" | ">>" | "<<" | "++" ; pattern -> "_" | record_pattern | variant_pattern | identifier ; record_pattern -> "{" ( identifier ( "=" pattern )? ( "," identifier ( "=" pattern )? )* ) ( "|" identifier ) "}" variant_pattern -> "`" identifier ( "(" ( "_" | compound_pattern | identifier ) ")" )? ; let -> "let" pattern "=" expression ( "and" pattern "=" expression )* "in" expression ; control -> | if | when if -> "if" expression "then" expression "else" expression ; when -> "when" expression "is" ( pattern "=>" expression )+ ; compound -> variant | record | list ; variant -> "`" identifier ( "(" expression ")" )? ; base_record -> expression ( "with" identifier "=" expression ( "," "with" identifier "=" expression )* )? record -> "{" ( identifier ("=" expression)? ( "," identifier ("=" expression)? )* )? ( "|" base_record )* "}" ; list -> "[" ( expression ( "," expression )* )? "]" ; field -> expression "." identifier ; index -> expression "[" expression "]" ; identifier -> IDENTIFIER | "@" STRING ; primary -> NUMBER | STRING | identifier | "(" expression ")" ;