add parser for class and function

 def func_name(params):
     ------------------
     func

 func-> id '(' params ')'
 */

/*

 params-> value ',' params
       -> value

 a.value
 a.length()
 a.value.length()

 a.value.length()
 ( ((a)(value)) (func length))

 where . is found from behind

 class_property-> class_property '.' id     // a.length
                | class_property '.' func   // a.length()
                | id

=======
change value to
//------ VALUE ------
 value    ->num
 | id
 | string
 | list
 | table
 | func
 | class_property
 | expr