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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> {
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;
}
}
/**
* 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>
fromLeft(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>
fromRight(RightType right) {
return new Either<>(null, right);
}
@Override
public <BoundLeft, BoundRight> IPair<BoundLeft, BoundRight> bind(
BiFunction<LeftType, RightType, IPair<BoundLeft, BoundRight>> binder) {
return binder.apply(leftVal, rightVal);
}
@Override
public <BoundLeft> IPair<BoundLeft, RightType> bindLeft(
Function<LeftType, IPair<BoundLeft, RightType>> leftBinder) {
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 (isLeft) {
return new Either<>(leftVal, null);
}
return rightBinder.apply(rightVal);
}
@Override
public <NewLeft> IPair<NewLeft, RightType>
mapLeft(Function<LeftType, NewLeft> mapper) {
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 (isLeft) {
return new Either<>(leftVal, null);
}
return new Either<>(null, mapper.apply(rightVal));
}
@Override
public <MergedType> MergedType
merge(BiFunction<LeftType, RightType, MergedType> merger) {
return merger.apply(leftVal, 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 (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));
});
}
}
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