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  Syntax of Mini-Pascal (Welsh & McKeag, 1980)
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   Syntax in recursive descent order
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   <program> ::= program <identifier> ; <block> .

   <block> ::= <variable declaration part>
   <procedure declaration part>
   <statement part>
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   <variable declaration part> ::= <empty> |
   var <variable declaration> ;
       { <variable declaration> ; }

   <variable declaration> ::= <identifier > { , <identifier> } : <type>

   <type> ::= <simple type> | <array type>

   <array type> ::= array [ <index range> ] of <simple type>

   <index range> ::= <integer constant> .. <integer constant>

   <simple type> ::= <type identifier>

   <type identifier> ::= <identifier>
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   <procedure declaration part> ::= { <procedure declaration> ; }

   <procedure declaration> ::= procedure <identifier> ; <block>
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   <statement part> ::= <compound statement>

   <compound statement> ::= begin <statement>{ ; <statement> } end

   <statement> ::= <simple statement> | <structured statement>
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   <simple statement> ::= <assignment statement> | <procedure statement> |
   <read statement> | <write statement>

   <assignment statement> ::= <variable> := <expression>

   <procedure statement> ::= <procedure identifier>

   <procedure identifier> ::= <identifier>

   <read statement> ::= read ( <input variable> { , <input variable> } )

   <input variable> ::= <variable>

   <write statement> ::= write ( <output value> { , <output value> } )

   <output value> ::= <expression>
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   <structured statement> ::= <compound statement> | <if statement> |
   <while statement>

   <if statement> ::= if <expression> then <statement> |
   if <expression> then <statement> else <statement>

   <while statement> ::= while <expression> do <statement>
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   <expression> ::= <simple expression> |
   <simple expression> <relational operator> <simple expression>

   <simple expression> ::= <sign> <term> { <adding operator> <term> }

   <term> ::= <factor> { <multiplying operator> <factor> }

   <factor> ::= <variable> | <constant> | ( <expression> ) | not <factor>
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   <relational operator> ::= = | <> | < | <= | >= | >

   <sign> ::= + | - | <empty>

   <adding operator> ::= + | - | or

   <multiplying operator> ::= * | div | and
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   <variable> ::= <entire variable> | <indexed variable>

   <indexed variable> ::= <array variable> [ <expression> ]

   <array variable> ::= <entire variable>

   <entire variable> ::= <variable identifier>

   <variable identifier> ::= <identifier>
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   Lexical grammar
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   <constant> ::= <integer constant> | <character constant> | <constant
   identifier>

   <constant identifier> ::= <identifier>

   <identifier> ::= <letter> { <letter or digit> }

   <letter or digit> ::= <letter> | <digit>

   <integer constant> ::= <digit> { <digit> }

   <character constant> ::= '< any character other than ' >'  |  ''''

   <letter> ::= a | b | c | d | e | f | g | h | i | j | k | l | m | n | o
   |
   p | q | r | s | t | u | v | w | x | y | z | A | B | C |
   D | E | F | G | H | I | J | K | L | M | N | O | P
   | Q | R | S | T | U | V | W | X | Y | Z

   <digit> ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

   <special symbol> ::= + | - | * | = | <> | < | > | <= | >= |
   ( | ) | [ | ] | := | . | , | ; | : | .. | div | or |
   and | not | if | then | else | of | while | do |
   begin | end | read | write | var | array |
   procedure | program

   <predefined identifier> ::= integer | Boolean | true | false
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