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;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  /**
   * Represents an integer in modular arithmetic.
   * Its {@code value} is between 0 and {@code m - 1} for some modulus {@code m}.
   *
   * <p>This object is immutable; all operations create a new object.
   */
  class ModularInteger {
    private final int value;
    private final int modulus;
  
    /** Creates a ModularInteger. */
    ModularInteger(int value, int modulus) {
      checkArgument(value >= 0 && value < modulus);
      this.value = value;
      this.modulus = modulus;
    }
  
    @Override public boolean equals(@Nullable Object obj) {
      return obj == this
          || obj instanceof ModularInteger
          && value == ((ModularInteger) obj).value
          && modulus == ((ModularInteger) obj).modulus;
    }
  
    @Override public int hashCode() {
      // 8191 is prime and, as 2^13 - 1, can easily be multiplied by bit-shifting
      return value + 8191 * modulus;
    }
  
    public int get() {
      return this.value;
    }
  
    public ModularInteger plus(int operand) {
      if (operand < 0) {
        return minus(Math.abs(operand));
      }
      return new ModularInteger((value + operand) % modulus, modulus);
    }
  
    public ModularInteger minus(int operand) {
      assert operand >= 0;
      int r = value - operand;
      while (r < 0) {
        r = r + modulus;
      }
      return new ModularInteger(r, modulus);
    }
  
    @Override public String toString() {
      return value + " mod " + modulus;
    }
  }
  