keyword ::= WHERE SELECT FROM ;

symbolic ::= 
  GE ">="  EQ "="  LE "<="  GT ">"   NE "!=" LT "<"  Comma "," ;

lexer INT ::= {:-?[0-9]:};
lexer ID ::= {:[a-zA-Z]+:};
ignore ::= {:[ \t\n]:};
lexer error ::= {:.:};

/* extremely simplified SQL grammar */
SelectStatement super SQLAST ::= T_Keyword_SELECT Columns 
                              T_Keyword_FROM Tables 
                              T_Keyword_WHERE WhereExpression ;
    {:  public void accept(SQLASTvisitor visitor) { visitor.visit(this); } :}

abstract Columns super SQLAST
    ColumnList super Columns ::= [ ColumnRecur ] Column ;
        {:  public void accept(SQLASTvisitor visitor) { 
                visitor.visit(this); } :}
    ColumnRecur super Columns ::= ColumnList T_Symbolic_Comma ;
        {:  public void accept(SQLASTvisitor visitor) { 
                visitor.visit(this); } :}
;

Column ::= T_ID ;

abstract Tables super SQLAST
    TableList super Tables ::= [ TableRecur ] Table;
        {:  public void accept(SQLASTvisitor visitor) { 
                visitor.visit(this); } :}
    TableRecur super Tables ::= TableList T_Symbolic_Comma ;
        {:  public void accept(SQLASTvisitor visitor) { 
                visitor.visit(this); } :}
;

Table ::= T_ID ;

abstract WhereExpression super SQLAST
    IntFilterExpression super WhereExpression ::= T_INT Binop Column ;
        {:  public void accept(SQLASTvisitor visitor) { 
                visitor.visit(this); } :}
    ColumnFilterExpression super WhereExpression ::= Column Binop T_INT ;
        {:  public void accept(SQLASTvisitor visitor) { 
                visitor.visit(this); } :}
    JoinExpression super WhereExpression ::= Column T_Symbolic_EQ RightColumn ;
        {:  public void accept(SQLASTvisitor visitor) { 
                visitor.visit(this); } :}
;