program         -> PROGRAM IS body ';'
body            -> {declaration} BEGIN {statement} END
declaration     -> VAR {var-decl}
                -> TYPE {type-decl}
                -> PROCEDURE {procedure-decl}
var-decl        -> ID { ',' ID } [ ':' typename ] ':=' expression ';' 
type-decl       -> ID IS type ';' 
procedure-decl  -> ID formal-params [':' typename] IS body ';'
typename        -> ID
type            -> ARRAY OF typename
                -> RECORD component {component} END
component       -> ID ':' typename ';'
formal-params   -> '(' fp-section {';' fp-section } ')' 
                -> '(' ')' 
fp-section      -> ID {',' ID} ':' typename
statement       -> lvalue ':=' expression ';'
                -> ID actual-params ';'
                -> READ '(' lvalue {',' lvalue} ')' ';'
                -> WRITE write-params ';'
                -> IF expression THEN {statement}
                   {ELSIF expression THEN {statement}}
                   [ELSE {statement}] END ';'
                -> WHILE expression DO {statement} END ';'
                -> LOOP {statement} END ';'
                -> FOR ID ':=' expression TO expression [ BY expression ] 
                   DO {statement} END ';'
                -> EXIT ';'
                -> RETURN [expression] ';'
write-params    -> '(' write-expr {',' write-expr } ')'
                -> '(' ')'
write-expr      -> STRING
                -> expression
expression      -> number
                -> lvalue
                -> '(' expression ')'
                -> unary-op expression
                -> expression binary-op expression
                -> ID actual-params
                -> ID record-inits
                -> ID array-inits
lvalue          -> ID
                -> lvalue '[' expression ']'
                -> lvalue '.' ID
actual-params   -> '(' expression {',' expression} ')'
                -> '(' ')'
record-inits    -> '{' ID ':=' expression { ';' ID ':=' expression} '}'
array-inits     -> '[<' array-init { ',' array-init } '>]'
array-init      -> [ expression 'OF' ] expression
number          -> INTEGER | REAL
unary-op        -> '+' | '-' | NOT
binary-op       -> '+' | '-' |  '*' | '/' | DIV | MOD | OR | AND
                -> '>' | '<' | '=' | '>=' | '<=' | '<>'