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Yacc constuction types (with error handling)

Optional Sequence  ( x := 0 or more `y' )

        x : /* empty */
            { EMPTY_X_LIST(); }
          | x y
            { ADD_Y_TO_X_LIST(); yyerrok; }
          | x error
          ;


Sequence    ( x := 1 or more `y' )     EG:  a b c d e

        x : y
            { EMPTY_X_LIST(); ADD_Y_TO_X_LIST(); }
          | x y
            { ADD_Y_TO_X_LIST(); yyerrok; }
          | error
          | x error
          ;


Separated List  (  x := y { T y } )    EG:  1,2,3,4

        x : y
            { EMPTY_X_LIST(); ADD_Y_TO_X_LIST(); }
          | x T y
            { ADD_Y_TO_X_LIST(); yyerrok; }
          | error
          | x error
          | x error y
            { ADD_Y_TO_X_LIST(); yyerrok; }
          | x T error
          ;

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