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.linq4j.tree;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.lang.reflect.Modifier;
  import java.lang.reflect.Type;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Represents a named parameter expression.
   */
  public class ParameterExpression extends Expression {
    private static final AtomicInteger SEQ = new AtomicInteger();
  
    public final int modifier;
    public final String name;
  
    public ParameterExpression(Type type) {
      this(0, type, "p" + SEQ.getAndIncrement());
    }
  
    public ParameterExpression(int modifier, Type type, String name) {
      super(ExpressionType.Parameter, type);
      checkArgument(Character.isJavaIdentifierStart(name.charAt(0)),
          "parameter name should be valid java identifier: %s. "
              + "The first character is invalid.",
          name);
      this.modifier = modifier;
      this.name = requireNonNull(name, "name");
    }
  
    @Override public Expression accept(Shuttle shuttle) {
      return shuttle.visit(this);
    }
  
    @Override public <R> R accept(Visitor<R> visitor) {
      return visitor.visit(this);
    }
  
    @Override public @Nullable Object evaluate(Evaluator evaluator) {
      return evaluator.peek(this);
    }
  
    @Override void accept(ExpressionWriter writer, int lprec, int rprec) {
      writer.append(name);
    }
  
    String declString() {
      return declString(type);
    }
  
    String declString(Type type) {
      final String modifiers = Modifier.toString(modifier);
      return modifiers + (modifiers.isEmpty() ? "" : " ") + Types.className(type)
          + " " + name;
    }
  
    @Override public boolean equals(@Nullable Object o) {
      return this == o;
    }
  
    @Override public int hashCode() {
      return System.identityHashCode(this);
    }
  }
  