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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.optics;
import static bjc.optics.Lenses.immutable;
import java.util.function.Function;
/**
* A type-variant lens
*
* @author Ben Culkin
*
* @param <W1> The first type the lens is used on
* @param <W2> The second 'whole' type
* @param <P1> The first 'part' type
* @param <P2> The second 'part' type
*/
public interface LensX<W1, W2, P1, P2> extends Optic<W1, W2, P1, P2> {
/**
* Retrieve the focused value of this lens.
*
* @param source The item to use the lens on.
*
* @return The value from the given whole this lens focuses on.
*/
P1 get(W1 source);
/**
* Create an updated version of the item this lens focuses on.
*
* @param source The item to use the lens on.
* @param val The new value.
*
* @return The updated item the lens was used on.
*/
W2 set(W1 source, P2 val);
/**
* Update the focused value.
*
* NOTE: It will often be more efficient to implement this directly. The
* implementation here is provided for convenience.
*
* @param source The item to use the lens on.
* @param action The action to applied to the focused item.
*
* @return The updated item the lens was used on.
*/
default W2 update(W1 source, Function<P1, P2> action) {
return set(source, action.apply(get(source)));
}
/**
* Compose two type-variant lenses together.
*
* @param <V1> The first type the second lens focuses on
* @param <V2> The second type the second lens focuses on.
*
* @param other The second lens to use.
*
* @return A lens composed from this one and the given one.
*/
default <V1, V2> LensX<W1, W2, V1, V2> compose(LensX<P1, P2, V1, V2> other) {
return immutable((whole) -> other.get(get(whole)),
(whole, val) -> update(whole, (P1 val2) -> other.set(val2, val)));
}
}
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