content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.calcite.sql.fun;
  
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlSpecialOperator;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  
  /**
   * An internal operator that throws an exception.
   *
   * <p>The exception is thrown with a (localized) error message which is the only
   * input parameter to the operator.
   *
   * <p>The return type is defined as a <code>BOOLEAN</code> to facilitate the use
   * of it in constructs such as the following:
   *
   * <blockquote><code>CASE<br>
   * WHEN &lt;condition&gt; THEN true<br>
   * ELSE throw("what's wrong with you man?")<br>
   * END</code></blockquote>
   */
  public class SqlThrowOperator extends SqlSpecialOperator {
    //~ Constructors -----------------------------------------------------------
  
    public SqlThrowOperator() {
      super(
          "$throw",
          SqlKind.OTHER,
          2,
          true,
          ReturnTypes.BOOLEAN,
          null,
          OperandTypes.CHARACTER);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void unparse(
        SqlWriter writer,
        SqlCall call,
        int leftPrec,
        int rightPrec) {
      final SqlWriter.Frame frame = writer.startFunCall(getName());
      call.operand(0).unparse(writer, 0, 0);
      writer.endFunCall(frame);
    }
  }
  