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/*
* esodata - data structures 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 java.util.Optional;
import bjc.data.Either;
/**
* Various utilities for working with prisms
*
* @author bjcul
*
*/
public class Prisms {
/**
* Create a prism that reflects on the value in an optional
*
* @param <L> The type contained in the optional
* @param <R> An auxiliary type
*
* TODO: better notes for what R is for
*
* @return A prism that reflects on an optional
*/
public static <L, R> PrismX<L, R, Optional<L>, Optional<R>> optional() {
return PrismX.of((opt) -> opt.isPresent() ? Either.right(opt.get()) : Either.left(Optional.empty()),
Optional::ofNullable);
}
/**
* Create a prism that reflects on whether a double corresponds to a given
* integer.
*
* @return A prism on the int view of a double.
*/
public static Prism<Integer, Double> whole() {
return Prism.of((vl) -> Math.rint(vl) == vl ? Either.right(vl.intValue()) : Either.left(vl),
Integer::doubleValue);
}
}
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