'parameter_list  : parameter_declaration
| parameter_list COMMA parameter_declaration'

def p_parameter_list(self, p):

    if (len(p) == 2):
        p[0] = c_ast.ParamList([p[1]], p[1].coord)
    else:
        p[1].params.append(p[3])
        p[0] = p[1]
