ast				=	  term 
					| "\", {ident, [":", tagged type], ","}, ident, [":", tagged type], ".", ast
					| "let", {ident, [":", tagged type], ":=", ast, ","}, ident, [":", tagged type], ":=", ast, [","], "in", ast ;

term			=	  ident 
					| constant 
					| "(", ast, ")" 
					| term, term ;

constant		=	nat | float | bool ;

tagged type		=	  type tag, ident 
					| type tag, ident, "=>", tagged type 
					| type ;

type tag		=	"Num" | "Any" ;

type			=	basic type | arrow type ;

basic type		=	"Nat" | "Float" | "Bool" | ident ;

arrow type		=	  "(", type, ")", "->", type
					| basic type, "->", type ;