1/*
2 * Copyright (C) 2010 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.caliper.util;
18
19import com.google.common.annotations.GwtCompatible;
20
21@GwtCompatible
22public class LinearTranslation {
23  //  y = mx + b
24  private final double m;
25  private final double b;
26
27  // TODO(kevinb): why so high? why even check this at all?
28  private static final double EQUALITY_TOLERANCE = 1.0E-6;
29
30  /**
31   * Constructs a linear translation for which {@code translate(in1) == out1}
32   * and {@code translate(in2) == out2}.
33   *
34   * @throws IllegalArgumentException if {@code in1 == in2}
35   */
36  public LinearTranslation(double in1, double out1, double in2, double out2) {
37    if (Math.abs(in1 - in2) < EQUALITY_TOLERANCE) {
38      throw new IllegalArgumentException("in1 and in2 are approximately equal");
39    }
40    double divisor = in1 - in2;
41    this.m = (out1 - out2) / divisor;
42    this.b = (in1 * out2 - in2 * out1) / divisor;
43  }
44
45  public double translate(double in) {
46    return m * in + b;
47  }
48}
49