class Id.
  token : "{letter}({letter}|{digit})*".
end class Id.

class Operator.
  token : defined in subclass.
  of Integer1 and Integer2 : defined in subclass.
end class Operator.

class RelOp extends Operator.

  token : <; <=; >; >=; =; <>.

  of Integer1 and Integer2 : Lexeme = <, Integer1 < Integer2.
  of Integer1 and Integer2 : Lexeme = <=, Integer1 <= Integer2.
  of Integer1 and Integer2 : Lexeme = >, Integer1 > Integer2.
  of Integer1 and Integer2 : Lexeme = >=, Integer1 >= Integer2.
  of Integer1 and Integer2 : Lexeme = =, Integer1 = Integer2.
  of Integer1 and Integer2 : Lexeme = <>, Integer1 != Integer2.

end class RelOp.

class ArithmeticOperator extends Operator.
end class ArithmeticOperator.

class AddOp extends ArithmeticOperator.
  token : +; -.
  of Integer1 and Integer2 : Lexeme = +, Integer1 + Integer2.
  of Integer1 and Integer2 : Lexeme = -, Integer1 + Integer2.
end class AddOp.

class MultOp extends ArithmeticOperator.
  token : *; /.
  of Integer1 and Integer2 : Lexeme = *, Integer1 * Integer2.
  of Integer1 and Integer2 : Lexeme = /, Integer2 = 0, Integer1 / Integer2.
end class MultOp.

class Store.
  StoreMap :: map Id to Integer.
  access with Id : apply StoreMap to Id.
  update Id with Integer : update StoreMap with Id mapped to Integer.
end class Store.

class File extends IntegerList.
end class File.

class Configuration.
  Store :: Store.
  InputFile, OutputFile :: File.
end class Configuration.

class Program.

  InputFile, OutputFile :: File.

  Syntax :: Series '.'.

  semantics with InputFile : 
    Configuration new InputFile,
    Series semantics with Configuration,
    Configuration getOutputFile.

end class Program.

class Series.

  Syntax :: Statement; Series ';' Statement.

  semantics with Configuration : 
    isSyntax Statement, 
      Statement semantics with Configuration;
    isSyntax Series ';' Statement, 
      Series semantics with Configuration,
      Statement semantics with Configuration.

end class Series.

class Statement.

  InputFile, OutputFile :: File.

  Syntax :: IOStatement; AssignStatement; IfThenStatement; 
    ToStatement; WhileStatement.

  extractConfigurationComponents :
    Store := Configuration getStore, 
    InputFile := Configuration getInputFile,
    OutputFile := Configuration getOutputFile.

  semantics with Configuration : defined in subclass.

end class Statement.

class IOStatement extends Statement.

  IdListHead :: Id.
  IdListTail :: IdList.

  Syntax :: read Ids; write Ids.

  semantics with Configuration :
    extractConfigurationComponents,
    IdList := semantics of Ids,
    io IdList.

  io IdList :
    isSyntax read Ids, 
      read IdList with Store and InputFile,
      Configuration setStore Store,
      Configuration setInputFile InputFile;
    isSyntax write Ids, 
      write IdList with Store and OutputFile,
      Configuration setOutputFile OutputFile;

  read Empty with Store and InputFile.
    
  read Id IdList with Store and InputFile :
    InputFile != Empty,
    Integer := InputFile head,
    Store update Id with Integer,
    InputFile := InputFile tail,
    read IdList with Store and InputFile.

  write Empty with Store and OutputFile.

  write Id IdList with Store and OutputFile :
    Integer := Store access Id,
    OutputFile := OutputFile append list Integer,
    write IdList with Store and OutputFile.
    
end IOStatement.

class Ids.

  Syntax :: Id; Ids ',' Id.

  semantics :
    isSyntax Id, list Id;
    isSyntax Ids ',' Id, IdList := Ids semantics, IdList append list Id.

end class Ids.

class AssignStatement extends Statement.

  Syntax :: Id := Expression.

  semantics with Configuration :
    extractConfigurationComponents,
    Integer := semantics of Expression with Store,
    Store update Id with Integer,
    Configuration setStore Store.

end class AssignStatement.

class ConditionalSemantics.
  semantics of conditional :
    semantics of condition, semantics of then part;
    semantics of condition failure, semantics of else part.
  semantics of condition : defined in subclass.
  semantics of condition fails : not semantics of condition.
  semantics of then part : defined in subclass.
  semantics of else part.
end class ConditionalSemantics.

class IfThenStatement extends Statement, ConditionalSemantics.

  Syntax :: if Comparison then Series fi.

  semantics with Configuration :
    extractConfigurationComponents,
    semantics of conditional.

  semantics of condition : semantics of Comparison with Store.

  semantics of then part : semantics of Series with Configuration.

end class IfThenStatement.

class IfThenElseStatement extends IfThenStatement.

  Syntax :: if Comparison then Series else Series1 fi.

  semantics with Configuration : 
    extractConfigurationComponents,
    semantics of conditional.

  semantics of else part : semantics of Series1 with Configuration.

end IfThenElseStatement.

class LoopSemantics.
  semantics of pretest loop :
    semantics of condition,
    semantics of loop body,
    semantics of pretest loop.
  semantics of posttest loop :
    semantics of loop body,
    semantics of condition,
    semantics of posttest loop.
  semantics of condition : defined in subclass.
  semantics of loop body : defined in subclass.
end class LoopSemantics.

class ToStatement extends Statement, LoopSemantics.

  RepetitionFactor :: Integer.

  Syntax :: to Expression do Series end.

  semantics with Configuration :
    extractConfigurationComponents,
    RepetitionFactor := semantics of Expression with Store,
    semantics of posttest loop.

  semantics of condition : RepetitionFactor > 0.

  semantics of loop body : 
    semantics of Series with Configuration,
    RepetitionFactor := RepetitionFactor - 1.

end class ToStatement.

class WhileStatement extends Statement, LoopSemantics.

  Syntax :: while Comparison do Series end.

  semantics with Configuration :
    extractConfigurationComponents,
    semantics of pretest loop.

  semantics of condition : semantics of Comparison with Store.

  semantics of loop body : semantics of Series with Configuration.

end class WhileStatement.

class Operation.

  Syntax :: Expression1 Operator Expression2.

  semantics with Store :
    Integer1 := Expression1 semantics with Store,
    Integer2 := Expression2 semantics with Store,
    Operator of Integer1 and Integer2.

end class Operation.

class Comparison extends Operation.

  Syntax :: Expression1 RelOp Expression2.

end class Comparison.

class Expression extends Operation.

  Expression :: Expression ArithmeticOperator Expression; UnsignedInteger; Id.

  Syntax :: Expression1 AddOp Expression2; Expression1 MultOp Expression2;
    ( Expression ); UnsignedInteger; Id.

  precedence left AddOp.
  precedence left MultOp.

  semantics with Store :
    isSyntax Expression1 ArithmeticOperator Expression2, 
      super semantics with Store;
    isSyntax UnsignedInteger, UnsignedInteger;
    isSyntax Id, Store access with Id.

end class Expression.