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package bjc.funcdata.theory;
import java.util.function.Function;
/**
* A functor over a pair of heterogeneous types.
*
* @author ben
*
* @param <LeftType>
* The type stored on the 'left' of the pair.
*
* @param <RightType>
* The type stored on the 'right' of the pair.
*/
public interface Bifunctor<LeftType, RightType> {
/**
* Alias for functor mapping.
*
* @author EVE
*
* @param <OldLeft>
* The old left type.
*
* @param <OldRight>
* The old right type.
*
* @param <NewLeft>
* The new left type.
*
* @param <NewRight>
* The new right type.
*/
public interface BifunctorMap<OldLeft, OldRight, NewLeft, NewRight>
extends Function<Bifunctor<OldLeft, OldRight>, Bifunctor<NewLeft, NewRight>> {
/*
* Alias
*/
}
/**
* Alias for left functor mapping.
*
* @author EVE
*
* @param <OldLeft>
* The old left type.
*
* @param <OldRight>
* The old right type.
*
* @param <NewLeft>
* The new left type.
*/
public interface LeftBifunctorMap<OldLeft, OldRight, NewLeft>
extends BifunctorMap<OldLeft, OldRight, NewLeft, OldRight> {
/*
* Alias
*/
}
/**
* Alias for right functor mapping.
*
* @author EVE
*
* @param <OldLeft>
* The old left type.
*
* @param <OldRight>
* The old right type.
*
* @param <NewRight>
* The new right type.
*/
public interface RightBifunctorMap<OldLeft, OldRight, NewRight>
extends BifunctorMap<OldLeft, OldRight, OldLeft, NewRight> {
/*
* Alias
*/
}
/**
* Lift a pair of functions to a single function that maps over both parts of a
* pair.
*
* @param <OldLeft>
* The old left type of the pair.
*
* @param <OldRight>
* The old right type of the pair.
*
* @param <NewLeft>
* The new left type of the pair.
*
* @param <NewRight>
* The new right type of the pair.
*
* @param leftFunc
* The function that maps over the left of the pair.
*
* @param rightFunc
* The function that maps over the right of the pair.
*
* @return A function that maps over both parts of the pair.
*/
public default <OldLeft, OldRight, NewLeft, NewRight>
BifunctorMap<OldLeft, OldRight, NewLeft, NewRight>
bimap(final Function<OldLeft, NewLeft> leftFunc,
final Function<OldRight, NewRight> rightFunc) {
final BifunctorMap<OldLeft, OldRight, NewLeft, NewRight> bimappedFunc
= argPair -> {
final LeftBifunctorMap<OldLeft, OldRight, NewLeft> leftMapper
= argPair.fmapLeft(leftFunc);
final Bifunctor<NewLeft, OldRight> leftMappedFunctor
= leftMapper.apply(argPair);
final RightBifunctorMap<NewLeft, OldRight, NewRight> rightMapper
= leftMappedFunctor.fmapRight(rightFunc);
return rightMapper.apply(leftMappedFunctor);
};
return bimappedFunc;
}
/**
* Lift a function to operate over the left part of this pair.
*
* @param <OldLeft>
* The old left type of the pair.
*
* @param <OldRight>
* The old right type of the pair.
*
* @param <NewLeft>
* The new left type of the pair.
*
* @param func
* The function to lift to work over the left side of the
* pair.
*
* @return The function lifted to work over the left side of bifunctors.
*/
public <OldLeft, OldRight, NewLeft> LeftBifunctorMap<OldLeft, OldRight, NewLeft>
fmapLeft(Function<OldLeft, NewLeft> func);
/**
* Lift a function to operate over the right part of this pair.
*
* @param <OldLeft>
* The old left type of the pair.
*
* @param <OldRight>
* The old right type of the pair.
*
* @param <NewRight>
* The new right type of the pair.
*
* @param func
* The function to lift to work over the right side of the
* pair.
*
* @return The function lifted to work over the right side of bifunctors.
*/
public <OldLeft, OldRight, NewRight> RightBifunctorMap<OldLeft, OldRight, NewRight>
fmapRight(Function<OldRight, NewRight> func);
/**
* Get the value contained on the left of this bifunctor.
*
* @return The value on the left side of this bifunctor.
*/
public LeftType getLeft();
/**
* Get the value contained on the right of this bifunctor.
*
* @return The value on the right of this bifunctor.
*/
public RightType getRight();
}
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