program -> 'BEGIN' statement_list 'END'.
statement_list -> statement statement_list2.
statement_list2 -> statement statement_list2
| .
statement -> ident ':=' expression ';'.
statement -> 'READ' '(' id_list ')' ';'.
statement -> 'WRITE' '(' expr_list ')' ';'.
statement -> 'IF' bexpr 'THEN' statement statement2.
statement2 -> 'ELSE' statement ';'
| ';'.
id_list -> ident id_list2.
id_list2 -> ',' id_list
| .
expr_list -> expression expr_list2.
expr_list2 ->  ',' expr_list expr_list2
| .
expression -> factor expression2.
expression2 -> '+' factor expression2
| '-' factor expression2
| .
factor -> '(' expression ')'
| ident
| number.
op -> '+'
| '-'.
bexpr -> bterm bexpr2.
bexpr2 -> 'OR' bterm bexpr2
| .
bterm -> bfactor bterm2.
bterm2 -> 'AND' bfactor bterm2
| .
bfactor -> 'NOT' bfactor
| '(' bexpr ')'
| 'TRUE'
| 'FALSE'.
ident -> letter S1.
S1 -> letter S1
| digit09 S1
| .
number -> digit19 Num
| op digit19 Num.
Num -> digit09 Num
| .
digit09 -> 0
| 1
| 2
| 3
| 4
| 5
| 6
| 7
| 8
| 9.
digit19 -> 1
| 2
| 3
| 4
| 5
| 6
| 7
| 8
| 9.
letter -> A
| Z.