1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
|
package bjc.utils.data;
import java.util.function.BiFunction;
import java.util.function.Function;
/**
* Represents a pair where only one side has a value
*
* @author ben
* @param <LeftType>
* The type that could be on the left
* @param <RightType>
* The type that could be on the right
*
*/
public class Either<LeftType, RightType> implements IPair<LeftType, RightType> {
/**
* Create a new either with the left value occupied
*
* @param <LeftType>
* The type of the left value
* @param <RightType>
* The type of the empty right value
* @param left
* The value to put on the left
* @return An either with the left side occupied
*/
public static <LeftType, RightType> Either<LeftType, RightType> left(LeftType left) {
return new Either<>(left, null);
}
/**
* Create a new either with the right value occupied
*
* @param <LeftType>
* The type of the empty left value
* @param <RightType>
* The type of the right value
* @param right
* The value to put on the right
* @return An either with the right side occupied
*/
public static <LeftType, RightType> Either<LeftType, RightType> right(RightType right) {
return new Either<>(null, right);
}
private LeftType leftVal;
private RightType rightVal;
private boolean isLeft;
private Either(LeftType left, RightType right) {
if(left == null) {
rightVal = right;
} else {
leftVal = left;
isLeft = true;
}
}
@Override
public <BoundLeft, BoundRight> IPair<BoundLeft, BoundRight> bind(
BiFunction<LeftType, RightType, IPair<BoundLeft, BoundRight>> binder) {
if(binder == null) throw new NullPointerException("Binder must not be null");
return binder.apply(leftVal, rightVal);
}
@Override
public <BoundLeft> IPair<BoundLeft, RightType> bindLeft(
Function<LeftType, IPair<BoundLeft, RightType>> leftBinder) {
if(leftBinder == null) throw new NullPointerException("Left binder must not be null");
if(isLeft) return leftBinder.apply(leftVal);
return new Either<>(null, rightVal);
}
@Override
public <BoundRight> IPair<LeftType, BoundRight> bindRight(
Function<RightType, IPair<LeftType, BoundRight>> rightBinder) {
if(rightBinder == null) throw new NullPointerException("Right binder must not be null");
if(isLeft) return new Either<>(leftVal, null);
return rightBinder.apply(rightVal);
}
@Override
public <OtherLeft, OtherRight, CombinedLeft, CombinedRight> IPair<CombinedLeft, CombinedRight> combine(
IPair<OtherLeft, OtherRight> otherPair,
BiFunction<LeftType, OtherLeft, CombinedLeft> leftCombiner,
BiFunction<RightType, OtherRight, CombinedRight> rightCombiner) {
if(otherPair == null)
throw new NullPointerException("Other pair must not be null");
else if(leftCombiner == null)
throw new NullPointerException("Left combiner must not be null");
else if(rightCombiner == null) throw new NullPointerException("Right combiner must not be null");
if(isLeft) return otherPair.bind((otherLeft, otherRight) -> {
return new Either<>(leftCombiner.apply(leftVal, otherLeft), null);
});
return otherPair.bind((otherLeft, otherRight) -> {
return new Either<>(null, rightCombiner.apply(rightVal, otherRight));
});
}
@Override
public <NewLeft> IPair<NewLeft, RightType> mapLeft(Function<LeftType, NewLeft> mapper) {
if(mapper == null) throw new NullPointerException("Mapper must not be null");
if(isLeft) return new Either<>(mapper.apply(leftVal), null);
return new Either<>(null, rightVal);
}
@Override
public <NewRight> IPair<LeftType, NewRight> mapRight(Function<RightType, NewRight> mapper) {
if(mapper == null) throw new NullPointerException("Mapper must not be null");
if(isLeft) return new Either<>(leftVal, null);
return new Either<>(null, mapper.apply(rightVal));
}
@Override
public <MergedType> MergedType merge(BiFunction<LeftType, RightType, MergedType> merger) {
if(merger == null) throw new NullPointerException("Merger must not be null");
return merger.apply(leftVal, rightVal);
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + (isLeft ? 1231 : 1237);
result = prime * result + ((leftVal == null) ? 0 : leftVal.hashCode());
result = prime * result + ((rightVal == null) ? 0 : rightVal.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if(this == obj) return true;
if(obj == null) return false;
if(getClass() != obj.getClass()) return false;
Either<?, ?> other = (Either<?, ?>) obj;
if(isLeft != other.isLeft) return false;
if(leftVal == null) {
if(other.leftVal != null) return false;
} else if(!leftVal.equals(other.leftVal)) return false;
if(rightVal == null) {
if(other.rightVal != null) return false;
} else if(!rightVal.equals(other.rightVal)) return false;
return true;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("Either [");
if(leftVal != null) {
builder.append("leftVal=");
builder.append(leftVal);
builder.append(", ");
}
if(rightVal != null) {
builder.append("rightVal=");
builder.append(rightVal);
builder.append(", ");
}
return builder.toString();
}
}
|
