parsing - Recursive Descent Parser using Python and PLY -


i apologize basic question but, i'm struggling here. need make recursive descent parser. i'm working in python , using ply. grammar follows:

< list > → (< sequence >) | ()

< sequence > → < listelement > , < sequence > | < listelement >

< listelement > → < list > | number

would this? way off? end goal read list data structure , print out.

 def p_list(p)     'list : "("sequence")" | "("")"'  def p_sequence(p)     'sequence : list_el","sequence | list_el'  def p_list_el(p)     'list_el : list | number'

if wondering full solution i'll post shortly.

this how i'd it:

tokens = ("lbracket", "rbracket",           "integer", "float", "comma") # can add other tokens t_lbracket = r'\(' t_rbracket = r'\)' t_integer = r'\d+' t_float = r'\d+\.\d+' t_comma = r','  def p_list(p):     """list : lbracket sequence rbracket             | lbracket rbracket"""     if len(p) == 4:         p[0] = p[2]     else:         p[0] = none  def p_number(p):     """number : integer               | float"""     p[0] = p[1]  def p_sequence(p):     """sequence : list_el comma sequence                 | list_el"""     if len(p) == 4:         p[0] = p[1] + p[3]     else:         p[0] = p[1]          def p_list_el(p):     """list_el : number                | list"""     p[0] = p[1]

edit:
quick explanation on tokens: in script should boil down token or character you've defined (so it's legal add). specifying them tokens, it's easier read , work with.


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