[antlr-interest] What multiple alternative?

[John B. Brodie]

Greetings!

On 01/07/2012 03:30 AM, James Ladd wrote:
> array_constant
>    : '#' array
>    ;
>
> array
>    : '(' array_element* ')'
>    ;
>
> array_element
>    : WHITESPACE
>    | NUMBER
>    | symbol
>    | STRING
>    | CHARACTER_CONSTANT
>    | array
>    ;
>
> symbol_constant
>    : '#' symbol
>    ;
>
> symbol
>    :  IDENTIFIER
>    | BINARY_SELECTOR
>    | (KEYWORD)+
>    ;
>
>

you have two nested repetitions but no way to know when the inner ends 
and the outer resumes.
e.g. zero or more array_elements each of which may contain 1 or more 
KEYWORDS (via symbol).

consider the input: #(a:b:c:d:)

now is this a single array_element containing a single symbol having 4 
KEYWORDs?
or is this 4 array_elements each containing a single symbol having 1 
KEYWORD?
or is this 2 array_elements each containing a single symbol having 2 
KEYWORDs?
or is this 2 array_elements each containing 2 symbols each having 1 KEYWORD?
or is this 3 array_elements...... you get the idea i hope