input: complete_expression 
        | scalefactor complete_expression 
        | scalefactor WHITESPACE complete_expression 
        | division unit_expression 
        ;

complete_expression: product_of_units 
        | product_of_units division unit_expression 
        ;

product_of_units: unit_expression 
        | product_of_units product unit_expression 
        ;

unit_expression: term                                 
        // m(2) is m^2, not function application
        | STRING parenthesized_number 
        | function_application 
        | OPEN_P complete_expression CLOSE_P 
        ;

function_application: STRING OPEN_P complete_expression CLOSE_P 
        ;

scalefactor: LIT10 power numeric_power 
        | LIT10 SIGNED_INTEGER 
        ;

division: DIVISION;

term: unit 
        | unit numeric_power 
        | unit power numeric_power 
        ;

unit: STRING 
        ;

power: CARET
        | STARSTAR
        ;

numeric_power: integer 
        | 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 | DOT;