input: complete_expression 
        | scalefactor complete_expression 
        | scalefactor WHITESPACE complete_expression 
        ;

complete_expression: product_of_units 
        ;

product_of_units: unit_expression
        | division unit_expression 
        | product_of_units product unit_expression 
        | product_of_units division unit_expression 
        ;

unit_expression: term                                 
        | function_application 
        | OPEN_P complete_expression CLOSE_P 
        ;

function_application: STRING OPEN_P complete_expression CLOSE_P 
        ;

scalefactor: LIT10 power numeric_power 
        | LIT10 
        | FLOAT 
        ;

division: DIVISION | WHITESPACE DIVISION
        | WHITESPACE DIVISION WHITESPACE | DIVISION WHITESPACE;

term: unit 
        | unit power numeric_power 
        ;

unit: STRING 
        ;

power: STARSTAR;

numeric_power: UNSIGNED_INTEGER 
        | FLOAT 
        | parenthesized_number 
        ;

parenthesized_number: OPEN_P integer CLOSE_P 
        | OPEN_P FLOAT CLOSE_P 
        | OPEN_P integer division UNSIGNED_INTEGER CLOSE_P 
        ;

integer: SIGNED_INTEGER | UNSIGNED_INTEGER;

product: WHITESPACE | STAR | WHITESPACE STAR
       | WHITESPACE STAR WHITESPACE | STAR WHITESPACE;