expression ->
	| sequence
//	| apply
	| unary
	| binary
//	| let
	| compound
	| control
	| field
	| index
//	| identifier
	| primary

identifier -> IDENTIFIER | "@" STRING ;
grouping -> "(" expression ")" ;
unary -> ( "-" | "!" ) expression ;
binary -> expression operator expression ;
operator ->
	| "==" | "!=" | "<" | "<=" | ">" | ">="
	| "+" | "-" | "*" | "/"
//	| "|>" | "<|" | ">>" | "<<"
	| "++" ;
control ->
	| if
//	| when
if -> "if" expression "then" expression "else" expression ;
compound -> variant | record | list ;
variant -> "`" identifier ( "(" ( expression ( "," expression)* )? ")" )? ;
record ->
	"{" ( identifier "=" expression ( "," identifier "=" expression )* )? "}" ;
list -> "[" ( expression ( "," expression )* )? "]" ;
field -> expression "." identifier ;
index -> expression "[" expression "]" ;
primary -> NUMBER | STRING | "(" expression ")" ;