Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
FoldLeft |
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| 1.7777777777777777;1.778 | ||||
FoldLeft$FoldLeftHelper |
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| 1.7777777777777777;1.778 |
1 | /* | |
2 | * Licensed to the Apache Software Foundation (ASF) under one or more | |
3 | * contributor license agreements. See the NOTICE file distributed with | |
4 | * this work for additional information regarding copyright ownership. | |
5 | * The ASF licenses this file to You under the Apache License, Version 2.0 | |
6 | * (the "License"); you may not use this file except in compliance with | |
7 | * the License. You may obtain a copy of the License at | |
8 | * | |
9 | * http://www.apache.org/licenses/LICENSE-2.0 | |
10 | * | |
11 | * Unless required by applicable law or agreed to in writing, software | |
12 | * distributed under the License is distributed on an "AS IS" BASIS, | |
13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
14 | * See the License for the specific language governing permissions and | |
15 | * limitations under the License. | |
16 | */ | |
17 | package org.apache.commons.functor.core.algorithm; | |
18 | ||
19 | import java.io.Serializable; | |
20 | ||
21 | import org.apache.commons.functor.BinaryFunction; | |
22 | import org.apache.commons.functor.UnaryFunction; | |
23 | import org.apache.commons.functor.UnaryProcedure; | |
24 | import org.apache.commons.functor.generator.Generator; | |
25 | ||
26 | /** | |
27 | * Functional left-fold algorithm against the elements of a {@link Generator}. | |
28 | * Uses the seed object (if supplied) as the initial left-side argument to the {@link BinaryFunction}, | |
29 | * then uses the result of that evaluation as the next left-side argument, until the {@link Generator}'s | |
30 | * elements have been expended. | |
31 | * | |
32 | * @param <T> the returned evaluation type. | |
33 | * @version $Revision: 1171154 $ $Date: 2011-09-15 17:58:38 +0200 (Thu, 15 Sep 2011) $ | |
34 | */ | |
35 | 0 | public class FoldLeft<T> implements UnaryFunction<Generator<T>, T>, BinaryFunction<Generator<T>, T, T>, Serializable { |
36 | ||
37 | /** | |
38 | * serialVersionUID declaration. | |
39 | */ | |
40 | private static final long serialVersionUID = 2473542974105910450L; | |
41 | ||
42 | /** | |
43 | * Helper procedure. | |
44 | */ | |
45 | private static class FoldLeftHelper<T> implements UnaryProcedure<T> { | |
46 | private final BinaryFunction<? super T, ? super T, ? extends T> function; | |
47 | private T seed; | |
48 | private boolean started; | |
49 | ||
50 | /** | |
51 | * Create a seedless FoldLeftHelper. | |
52 | */ | |
53 | public FoldLeftHelper(BinaryFunction<? super T, ? super T, ? extends T> function) { | |
54 | 18 | this(null, function); |
55 | 18 | } |
56 | ||
57 | /** | |
58 | * Create a new FoldLeftHelper. | |
59 | * @param seed initial left-side argument | |
60 | */ | |
61 | 20 | FoldLeftHelper(T seed, BinaryFunction<? super T, ? super T, ? extends T> function) { |
62 | 20 | this.seed = seed; |
63 | 20 | started = seed != null ? true : false; |
64 | 20 | this.function = function; |
65 | 20 | } |
66 | ||
67 | /** | |
68 | * {@inheritDoc} | |
69 | */ | |
70 | public void run(T obj) { | |
71 | 308 | if (!started) { |
72 | 18 | seed = obj; |
73 | 18 | started = true; |
74 | } else { | |
75 | 290 | seed = function.evaluate(seed, obj); |
76 | } | |
77 | 308 | } |
78 | ||
79 | /** | |
80 | * Get current result. | |
81 | * @return Object | |
82 | */ | |
83 | T getResult() { | |
84 | 20 | return started ? seed : null; |
85 | } | |
86 | ||
87 | } | |
88 | ||
89 | private final BinaryFunction<? super T, ? super T, ? extends T> function; | |
90 | ||
91 | /** | |
92 | * Create a new FoldLeft. | |
93 | * @param func {@link BinaryFunction} to apply to each (seed, next) | |
94 | */ | |
95 | 18 | public FoldLeft(BinaryFunction<? super T, ? super T, ? extends T> func) { |
96 | 18 | this.function = func; |
97 | 18 | } |
98 | ||
99 | /** | |
100 | * {@inheritDoc} | |
101 | * @param obj {@link Generator} to transform | |
102 | */ | |
103 | public final T evaluate(Generator<T> obj) { | |
104 | 18 | FoldLeftHelper<T> helper = new FoldLeftHelper<T>(function); |
105 | 18 | obj.run(helper); |
106 | 18 | return helper.getResult(); |
107 | } | |
108 | ||
109 | /** | |
110 | * {@inheritDoc} | |
111 | * @param left {@link Generator} to transform | |
112 | * @param right initial left-side seed object | |
113 | */ | |
114 | public final T evaluate(Generator<T> left, T right) { | |
115 | 2 | FoldLeftHelper<T> helper = new FoldLeftHelper<T>(right, function); |
116 | 2 | left.run(helper); |
117 | 2 | return helper.getResult(); |
118 | } | |
119 | ||
120 | /** | |
121 | * {@inheritDoc} | |
122 | */ | |
123 | public boolean equals(Object obj) { | |
124 | 0 | if (obj == this) { |
125 | 0 | return true; |
126 | } | |
127 | 0 | if (!(obj instanceof FoldLeft<?>)) { |
128 | 0 | return false; |
129 | } | |
130 | 0 | return ((FoldLeft<?>) obj).function.equals(function); |
131 | } | |
132 | ||
133 | /** | |
134 | * {@inheritDoc} | |
135 | */ | |
136 | public int hashCode() { | |
137 | 0 | return "FoldLeft".hashCode() << 2 ^ function.hashCode(); |
138 | } | |
139 | ||
140 | } |