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package bjc.utils.graph;
import java.util.function.Function;
/**
* Holds a single value of a specific type. This is used for indirect
* references to data, and more specifically for accessing non-final
* variables from a lambda. AKA the identity monad
*
* @author ben
*
* @param <T>
* The type of the data being held
*/
public class GenHolder<T> {
/**
* The state this holder is responsible for.
*/
public T held;
/**
* Creates a new empty holder, with its state set to null
*/
public GenHolder() {
held = null;
}
/**
* Creates a new holder, with its state initialized to the provided
* value
*
* @param held
* The state to initialize this holder to.
*/
public GenHolder(T hld) {
held = hld;
}
/**
* Apply the given transformation to the held value. Returns the holder
* for allowing chaining of transforms
*
* @param f
* The transform to apply to the value
* @return The holder
*/
public GenHolder<T> transform(Function<T, T> f) {
held = f.apply(held);
return this;
}
/**
* Return the result of applying the given transformation to the held
* value Doesn't change the held value
*
* @param f
* The transformation to apply
* @return A holder with the transformed value
*/
public <NewT> GenHolder<NewT> map(Function<T, NewT> f) {
return new GenHolder<NewT>(f.apply(held));
}
/**
* Returns a raw mapped value, not contained in a GenHolder
*
* @param f
* The function to use for mapping the value
* @return The mapped value outside of a GenHolder
*/
public <E> E unwrap(Function<T, E> f) {
return f.apply(held);
}
}
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