digraph Grammar_diagram {
	graph [
		label="Grammar diagram"
		labelloc="t"
		fontname="Helvetica,Arial,sans-serif"
        // rankdir=LR
        // splines=ortho
	]
	node [
		fontname="Helvetica,Arial,sans-serif"
		// shape=record
		style=filled
		fillcolor=gray95
        
	]
    edge [
        
    ]
    START -> OPEN_BRACKET

    SIGN_PREFIX //[label="SIGN_PREFIX (unary operator)"]
    SIGN_PREFIX -> NUMBER

    OPEN_BRACKET -> NUMBER
    OPEN_BRACKET -> OPEN_BRACKET
    OPEN_BRACKET -> SIGN_PREFIX

    NUMBER -> BINARY_OPERATOR
    BINARY_OPERATOR -> NUMBER
    BINARY_OPERATOR -> OPEN_BRACKET

    NUMBER -> CLOSE_BRACKET
    CLOSE_BRACKET -> CLOSE_BRACKET
    CLOSE_BRACKET -> BINARY_OPERATOR
    CLOSE_BRACKET -> END
}