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/*
* esodata - data structures and other things, of varying utility
* Copyright 2022, Ben Culkin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bjc.data;
import java.util.function.Function;
import java.util.function.UnaryOperator;
/**
* Simple implementation of IHolder that has no hidden behavior.
*
* @author ben
*
* @param <ContainedType>
* The type contained in the holder.
*/
public class Identity<ContainedType> implements Holder<ContainedType> {
/* The held value. */
private ContainedType heldValue;
/** Create a holder holding null */
public Identity() {
heldValue = null;
}
/**
* Create a holder holding the specified value.
*
* @param value
* The value to hold.
*/
public Identity(final ContainedType value) {
heldValue = value;
}
@Override
public <BoundType> Holder<BoundType>
bind(final Function<ContainedType, Holder<BoundType>> binder) {
return binder.apply(heldValue);
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + (heldValue == null ? 0 : heldValue.hashCode());
return result;
}
@Override
public boolean equals(final Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (!(obj instanceof Identity)) return false;
final Identity<?> other = (Identity<?>) obj;
if (heldValue == null) {
if (other.heldValue != null) return false;
} else if (!heldValue.equals(other.heldValue)) {
return false;
}
return true;
}
@Override
public <NewType> Function<ContainedType, Holder<NewType>>
lift(final Function<ContainedType, NewType> func) {
return val -> {
return new Identity<>(func.apply(val));
};
}
@Override
public <MappedType> Holder<MappedType>
map(final Function<ContainedType, MappedType> mapper) {
return new Identity<>(mapper.apply(heldValue));
}
@Override
public String toString() {
return String.format("Identity [heldValue=%s]", heldValue);
}
@Override
public Holder<ContainedType>
transform(final UnaryOperator<ContainedType> transformer) {
heldValue = transformer.apply(heldValue);
return this;
}
@Override
public <UnwrappedType> UnwrappedType
unwrap(final Function<ContainedType, UnwrappedType> unwrapper) {
return unwrapper.apply(heldValue);
}
/**
* Create a new identity container.
*
* @param <ContainedType> The type of the contained value.
* @param val The contained value.
*
* @return A new identity container.
*/
public static <ContainedType> Identity<ContainedType> id(final ContainedType val) {
return new Identity<>(val);
}
/**
* Create a new empty identity container.
*
* @param <ContainedType> The type of the contained value.
*
* @return A new empty identity container.
*/
public static <ContainedType> Identity<ContainedType> id() {
return new Identity<>();
}
}
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