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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.Consumer;
import java.util.function.Function;
import java.util.function.UnaryOperator;
import bjc.data.internals.BoundListHolder;
import bjc.data.internals.WrappedLazy;
import bjc.data.internals.WrappedOption;
import bjc.funcdata.FunctionalList;
import bjc.funcdata.theory.Functor;
/**
* A holder of a single value.
*
* @author ben
*
* @param <ContainedType>
* The type of value held.
*/
public interface Holder<ContainedType> extends Functor<ContainedType> {
/**
* Bind a function across the value in this container.
*
* @param <BoundType>
* The type of value in this container.
*
* @param binder
* The function to bind to the value.
*
* @return A holder from binding the value.
*/
public <BoundType> Holder<BoundType>
bind(Function<ContainedType, Holder<BoundType>> binder);
/**
* Apply an action to the value.
*
* @param action
* The action to apply to the value.
*/
public default void doWith(final Consumer<? super ContainedType> action) {
transform(value -> {
action.accept(value);
return value;
});
}
@Override
default <ArgType, ReturnType> Function<Functor<ArgType>, Functor<ReturnType>>
fmap(final Function<ArgType, ReturnType> func) {
return argumentFunctor -> {
if (!(argumentFunctor instanceof Holder<?>)) {
final String msg
= "This functor only supports mapping over instances of IHolder";
throw new IllegalArgumentException(msg);
}
final Holder<ArgType> holder = (Holder<ArgType>) argumentFunctor;
return holder.map(func);
};
}
@Override
public default ContainedType getValue() {
return unwrap(value -> value);
}
/**
* Lifts a function to bind over this holder.
*
* @param <NewType>
* The type of the functions return.
*
* @param func
* The function to lift over the holder.
*
* @return The function lifted over the holder.
*/
public <NewType> Function<ContainedType, Holder<NewType>>
lift(Function<ContainedType, NewType> func);
/**
* Make this holder lazy.
*
* @return A lazy version of this holder.
*/
public default Holder<ContainedType> makeLazy() {
return new WrappedLazy<>(this);
}
/**
* Make this holder a list.
*
* @return A list version of this holder.
*/
public default Holder<ContainedType> makeList() {
return new BoundListHolder<>(new FunctionalList<>(this));
}
/**
* Make this holder optional.
*
* @return An optional version of this holder.
*/
public default Holder<ContainedType> makeOptional() {
return new WrappedOption<>(this);
}
/**
* Create a new holder with a mapped version of the value in this holder.
*
* Does not change the internal state of this holder.
*
* @param <MappedType>
* The type of the mapped value.
*
* @param mapper
* The function to do mapping with.
*
* @return A holder with the mapped value
*/
public <MappedType> Holder<MappedType>
map(Function<ContainedType, MappedType> mapper);
/**
* Replace the held value with a new one.
*
* @param newValue
* The value to hold instead.
*
* @return The holder itself.
*/
public default Holder<ContainedType> replace(final ContainedType newValue) {
return transform(oldValue -> newValue);
}
/**
* Transform the value held in this holder.
*
* @param transformer
* The function to transform the value with.
*
* @return The holder itself, for easy chaining.
*/
public Holder<ContainedType> transform(UnaryOperator<ContainedType> transformer);
/**
* Unwrap the value contained in this holder so that it is no longer held.
*
* @param <UnwrappedType>
* The type of the unwrapped value.
*
* @param unwrapper
* The function to use to unwrap the value.
*
* @return The unwrapped held value.
*/
public <UnwrappedType> UnwrappedType
unwrap(Function<ContainedType, UnwrappedType> unwrapper);
/**
* Create an instace of IHolder containing a single value.
*
* @param <ElementType> The type of the value contained.
*
* @param contained The value to contain.
*
* @return An instance of IHolder containing that value.
*/
static <ElementType> Holder<ElementType> of(ElementType contained) {
return new Identity<>(contained);
}
}
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