fj.data.optic.Getter Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of functionaljava Show documentation
Show all versions of functionaljava Show documentation
Functional Java is an open source library that supports closures for the Java programming language
package fj.data.optic;
import fj.F;
import fj.Function;
import fj.Monoid;
import fj.P;
import fj.P2;
import fj.data.Either;
/**
* A {@link Getter} can be seen as a glorified get method between a type S and a type A.
*
* A {@link Getter} is also a valid {@link Fold}
*
* @param the source of a {@link Getter}
* @param the target of a {@link Getter}
*/
public abstract class Getter {
Getter() {
super();
}
/** get the target of a {@link Getter} */
public abstract A get(S s);
/** join two {@link Getter} with the same target */
public final Getter, A> sum(final Getter other) {
return getter(e -> e.either(this::get, other::get));
}
/** pair two disjoint {@link Getter} */
public final Getter, P2> product(final Getter other) {
return getter(p2 -> P.p(this.get(p2._1()), other.get(p2._2())));
}
public final Getter, P2> first() {
return getter(p -> P.p(this.get(p._1()), p._2()));
}
public final Getter, P2> second() {
return getter(p -> P.p(p._1(), this.get(p._2())));
}
/*************************************************************/
/** Compose methods between a {@link Getter} and another Optics */
/*************************************************************/
/** compose a {@link Getter} with a {@link Fold} */
public final Fold composeFold(final Fold other) {
return asFold().composeFold(other);
}
/** compose a {@link Getter} with a {@link Getter} */
public final Getter composeGetter(final Getter other) {
return getter(s -> other.get(get(s)));
}
/** compose a {@link Getter} with a {@link POptional} */
public final Fold composeOptional(final POptional other) {
return asFold().composeOptional(other);
}
/** compose a {@link Getter} with a {@link PPrism} */
public final Fold composePrism(final PPrism other) {
return asFold().composePrism(other);
}
/** compose a {@link Getter} with a {@link PLens} */
public final Getter composeLens(final PLens other) {
return composeGetter(other.asGetter());
}
/** compose a {@link Getter} with a {@link PIso} */
public final Getter composeIso(final PIso other) {
return composeGetter(other.asGetter());
}
/******************************************************************/
/** Transformation methods to view a {@link Getter} as another Optics */
/******************************************************************/
/** view a {@link Getter} with a {@link Fold} */
public final Fold asFold() {
return new Fold() {
@Override
public F foldMap(final Monoid m, final F f) {
return s -> f.f(get(s));
}
};
}
public static Getter id() {
return PIso. pId().asGetter();
}
public static final Getter, A> codiagonal() {
return getter(e -> e.either(Function.identity(), Function.identity()));
}
public static final Getter getter(final F get) {
return new Getter() {
@Override
public A get(final S s) {
return get.f(s);
}
};
}
}