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.rex;
  
  import com.google.common.collect.ImmutableList;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Visitor pattern for traversing a tree of {@link RexNode} objects
   * and passing a payload to each.
   *
   * @see RexVisitor
   *
   * @param <R> Return type
   * @param <P> Payload type
   */
  public interface RexBiVisitor<R, P> {
    //~ Methods ----------------------------------------------------------------
  
    R visitInputRef(RexInputRef inputRef, P arg);
  
    R visitLocalRef(RexLocalRef localRef, P arg);
  
    R visitLiteral(RexLiteral literal, P arg);
  
    R visitCall(RexCall call, P arg);
  
    R visitOver(RexOver over, P arg);
  
    R visitCorrelVariable(RexCorrelVariable correlVariable, P arg);
  
    R visitDynamicParam(RexDynamicParam dynamicParam, P arg);
  
    R visitRangeRef(RexRangeRef rangeRef, P arg);
  
    R visitFieldAccess(RexFieldAccess fieldAccess, P arg);
  
    R visitSubQuery(RexSubQuery subQuery, P arg);
  
    R visitTableInputRef(RexTableInputRef ref, P arg);
  
    R visitPatternFieldRef(RexPatternFieldRef ref, P arg);
  
    R visitLambda(RexLambda lambda, P arg);
  
    R visitNodeAndFieldIndex(RexNodeAndFieldIndex nodeAndFieldIndex, P arg);
  
    /** Visits a list and writes the results to another list. */
    default void visitList(Iterable<? extends RexNode> exprs, P arg,
        List<R> out) {
      for (RexNode expr : exprs) {
        out.add(expr.accept(this, arg));
      }
    }
  
    /** Visits a list and returns a list of the results.
     * The resulting list is immutable and does not contain nulls. */
    default List<R> visitList(Iterable<? extends RexNode> exprs, P arg) {
      final List<R> out = new ArrayList<>();
      visitList(exprs, arg, out);
      return ImmutableList.copyOf(out);
    }
  
    /** Visits a list of expressions. */
    default void visitEach(Iterable<? extends RexNode> exprs, P arg) {
      for (RexNode expr : exprs) {
        expr.accept(this, arg);
      }
    }
  
    /** Visits a list of expressions, passing the 0-based index of the expression
     * in the list.
     *
     * <p>Assumes that the payload type {@code P} is {@code Integer}. */
    default void visitEachIndexed(Iterable<? extends RexNode> exprs) {
      int i = 0;
      for (RexNode expr : exprs) {
        //noinspection unchecked
        expr.accept(this, (P) (Integer) i++);
      }
    }
  }
  