% Part I.  Syntax specification
define program
        [expression]
end define

define expression
        [term]
    |   [expression] [addop] [term]
end define

define term
        [primary]
    |   [term] [mulop] [primary]
end define

define primary 
        [number]
    |   ( [expression] )
end define

define addop
        '+
    |   '-
end define

define mulop
        '*
    |   '/
end define