How to make ANTLR consume all available elements using recursion?

问题

This is my grammar:

grammar test;

text: foo EOF;

foo:
    'X'
    |
    '('
    foo
    ')'
    |
    foo
    '!'
    |
    foo
    tail
    ;

tail: (' ' foo)+;

This is the input it perfectly parses:

X (X! (X)! (X X X)!!!) X

However, the output tree has too many tail elements, as I explained earlier here. Is it possible to fix this?

回答1:

Thanks to @kaby76, the solution is found:

foo:  
  'X' tail? 
  | 
  '(' foo ')' tail? 
  | 
  foo '!' tail? 
  ; 
tail: 
  (
    ' ' 'X' 
    | 
    ' ' '(' foo ')' 
    | 
    ' ' foo '!'
  )+ 
  ;

来源：https://stackoverflow.com/questions/64635366/how-to-make-antlr-consume-all-available-elements-using-recursion