expression ->
	| literal
//	| IDENTIFIER
//	| sequence
	| unary
	| binary
//	| let
//	| when
	| if
	| variant
	| record
	| list
	| field
	| index
	| grouping ;

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