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      1 grammar t022scopes;
      2 
      3 options {
      4     language=Python;
      5 }
      6 
      7 /* global scopes */
      8 
      9 scope aScope {
     10 names
     11 }
     12 
     13 a
     14 scope aScope;
     15     :   {$aScope::names = [];} ID*
     16     ;
     17 
     18 
     19 /* rule scopes, from the book, final beta, p.147 */
     20 
     21 b[v]
     22 scope {x}
     23     : {$b::x = v;} b2
     24     ;
     25 
     26 b2
     27     : b3
     28     ;
     29 
     30 b3 
     31     : {$b::x}?=> ID // only visible, if b was called with True
     32     | NUM
     33     ;
     34 
     35 
     36 /* rule scopes, from the book, final beta, p.148 */
     37 
     38 c returns [res]
     39 scope {
     40     symbols
     41 }
     42 @init {
     43     $c::symbols = set();
     44 }
     45     : '{' c1* c2+ '}'
     46         { $res = $c::symbols; }
     47     ;
     48 
     49 c1
     50     : 'int' ID {$c::symbols.add($ID.text)} ';'
     51     ;
     52 
     53 c2
     54     : ID '=' NUM ';'
     55         {
     56             if $ID.text not in $c::symbols:
     57                 raise RuntimeError($ID.text)
     58         }
     59     ;
     60 
     61 /* recursive rule scopes, from the book, final beta, p.150 */
     62 
     63 d returns [res]
     64 scope {
     65     symbols
     66 }
     67 @init {
     68     $d::symbols = set();
     69 }
     70     : '{' d1* d2* '}'
     71         { $res = $d::symbols; }
     72     ;
     73 
     74 d1
     75     : 'int' ID {$d::symbols.add($ID.text)} ';'
     76     ;
     77 
     78 d2
     79     : ID '=' NUM ';'
     80         {
     81             for s in reversed(range(len($d))):
     82                 if $ID.text in $d[s]::symbols:
     83                     break
     84             else:
     85                 raise RuntimeError($ID.text)
     86         }
     87     | d
     88     ;
     89 
     90 /* recursive rule scopes, access bottom-most scope */
     91 
     92 e returns [res]
     93 scope {
     94     a
     95 }
     96 @after {
     97     $res = $e::a;
     98 }
     99     : NUM { $e[0]::a = int($NUM.text); }
    100     | '{' e '}'
    101     ;
    102 
    103 
    104 /* recursive rule scopes, access with negative index */
    105 
    106 f returns [res]
    107 scope {
    108     a
    109 }
    110 @after {
    111     $res = $f::a;
    112 }
    113     : NUM { $f[-2]::a = int($NUM.text); }
    114     | '{' f '}'
    115     ;
    116 
    117 
    118 /* tokens */
    119 
    120 ID  :   ('a'..'z')+
    121     ;
    122 
    123 NUM :   ('0'..'9')+
    124     ;
    125 
    126 WS  :   (' '|'\n'|'\r')+ {$channel=HIDDEN}
    127     ;
    128