/* __ __ __ __ __ ___
* \ \ / / \ \ / / __/
* \ \/ / /\ \ \/ / /
* \____/__/ \__\____/__/.ɪᴏ
* ᶜᵒᵖʸʳᶦᵍʰᵗ ᵇʸ ᵛᵃᵛʳ ⁻ ˡᶦᶜᵉⁿˢᵉᵈ ᵘⁿᵈᵉʳ ᵗʰᵉ ᵃᵖᵃᶜʰᵉ ˡᶦᶜᵉⁿˢᵉ ᵛᵉʳˢᶦᵒⁿ ᵗʷᵒ ᵈᵒᵗ ᶻᵉʳᵒ
*/
package io.vavr;
/*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*\
G E N E R A T O R C R A F T E D
\*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
import static io.vavr.Function1Module.sneakyThrow;
import io.vavr.control.Option;
import io.vavr.control.Try;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.function.Function;
import java.util.function.Predicate;
/**
* Represents a function with one argument.
*
* @param <T1> argument 1 of the function
* @param <R> return type of the function
* @author Daniel Dietrich
*/
@FunctionalInterface
public interface Function1<T1, R> extends Lambda<R>, Function<T1, R> {
/**
* The <a href="https://docs.oracle.com/javase/8/docs/api/index.html">serial version uid</a>.
*/
long serialVersionUID = 1L;
/**
* Creates a {@code Function1} based on
* <ul>
* <li><a href="https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html">method reference</a></li>
* <li><a href="https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html#syntax">lambda expression</a></li>
* </ul>
*
* Examples (w.l.o.g. referring to Function1):
* <pre><code>// using a lambda expression
* Function1<Integer, Integer> add1 = Function1.of(i -> i + 1);
*
* // using a method reference (, e.g. Integer method(Integer i) { return i + 1; })
* Function1<Integer, Integer> add2 = Function1.of(this::method);
*
* // using a lambda reference
* Function1<Integer, Integer> add3 = Function1.of(add1::apply);
* </code></pre>
* <p>
* <strong>Caution:</strong> Reflection loses type information of lambda references.
* <pre><code>// type of a lambda expression
* Type<?, ?> type1 = add1.getType(); // (Integer) -> Integer
*
* // type of a method reference
* Type<?, ?> type2 = add2.getType(); // (Integer) -> Integer
*
* // type of a lambda reference
* Type<?, ?> type3 = add3.getType(); // (Object) -> Object
* </code></pre>
*
* @param methodReference (typically) a method reference, e.g. {@code Type::method}
* @param <R> return type
* @param <T1> 1st argument
* @return a {@code Function1}
*/
static <T1, R> Function1<T1, R> of(Function1<T1, R> methodReference) {
return methodReference;
}
/**
* Lifts the given {@code partialFunction} into a total function that returns an {@code Option} result.
*
* @param partialFunction a function that is not defined for all values of the domain (e.g. by throwing)
* @param <R> return type
* @param <T1> 1st argument
* @return a function that applies arguments to the given {@code partialFunction} and returns {@code Some(result)}
* if the function is defined for the given arguments, and {@code None} otherwise.
*/
@SuppressWarnings("RedundantTypeArguments")
static <T1, R> Function1<T1, Option<R>> lift(Function<? super T1, ? extends R> partialFunction) {
return t1 -> Try.<R>of(() -> partialFunction.apply(t1)).toOption();
}
/**
* Lifts the given {@code partialFunction} into a total function that returns an {@code Try} result.
*
* @param partialFunction a function that is not defined for all values of the domain (e.g. by throwing)
* @param <R> return type
* @param <T1> 1st argument
* @return a function that applies arguments to the given {@code partialFunction} and returns {@code Success(result)}
* if the function is defined for the given arguments, and {@code Failure(throwable)} otherwise.
*/
static <T1, R> Function1<T1, Try<R>> liftTry(Function<? super T1, ? extends R> partialFunction) {
return t1 -> Try.of(() -> partialFunction.apply(t1));
}
/**
* Narrows the given {@code Function<? super T1, ? extends R>} to {@code Function1<T1, R>}
*
* @param f A {@code Function1}
* @param <R> return type
* @param <T1> 1st argument
* @return the given {@code f} instance as narrowed type {@code Function1<T1, R>}
*/
@SuppressWarnings("unchecked")
static <T1, R> Function1<T1, R> narrow(Function<? super T1, ? extends R> f) {
return (Function1<T1, R>) f;
}
/**
* Returns the identity Function1, i.e. the function that returns its input.
*
* @param <T> argument type (and return type) of the identity function
* @return the identity Function1
*/
static <T> Function1<T, T> identity() {
return t -> t;
}
/**
* Applies this function to one argument and returns the result.
*
* @param t1 argument 1
* @return the result of function application
*
*/
R apply(T1 t1);
@Override
default int arity() {
return 1;
}
/**
* Returns a function that always returns the constant
* value that you give in parameter.
*
* @param <T1> generic parameter type 1 of the resulting function
* @param <R> the result type
* @param value the value to be returned
* @return a function always returning the given value
*/
static <T1, R> Function1<T1, R> constant(R value) {
return (t1) -> value;
}
@Override
default Function1<T1, R> curried() {
return this;
}
@Override
default Function1<Tuple1<T1>, R> tupled() {
return t -> apply(t._1);
}
@Override
default Function1<T1, R> reversed() {
return this;
}
@Override
default Function1<T1, R> memoized() {
if (isMemoized()) {
return this;
} else {
final Map<Tuple1<T1>, R> cache = new HashMap<>();
return (Function1<T1, R> & Memoized) (t1)
-> Memoized.of(cache, Tuple.of(t1), tupled());
}
}
/**
* Converts this {@code Function1} to a {@link PartialFunction} by adding an {@code isDefinedAt} condition.
* <p>
* @param isDefinedAt a predicate that states if an element is in the domain of the returned {@code PartialFunction}.
* @return a new {@code PartialFunction} that has the same behavior like this function but is defined only for those elements that make it through the given {@code Predicate}
* @throws NullPointerException if {@code isDefinedAt} is null
*/
default PartialFunction<T1, R> partial(Predicate<? super T1> isDefinedAt) {
Objects.requireNonNull(isDefinedAt, "isDefinedAt is null");
final Function1<T1, R> self = this;
return new PartialFunction<T1, R>() {
@Override
public boolean isDefinedAt(T1 t1) {
return isDefinedAt.test(t1);
}
@Override
public R apply(T1 t1) {
return self.apply(t1);
}
};
}
/**
* Returns a composed function that first applies this Function1 to the given argument and then applies
* {@linkplain Function} {@code after} to the result.
*
* @param <V> return type of after
* @param after the function applied after this
* @return a function composed of this and after
* @throws NullPointerException if after is null
*/
default <V> Function1<T1, V> andThen(Function<? super R, ? extends V> after) {
Objects.requireNonNull(after, "after is null");
return (t1) -> after.apply(apply(t1));
}
/**
* Returns a composed function that first applies the {@linkplain Function} {@code before} the
* given argument and then applies this Function1 to the result.
*
* @param <V> argument type of before
* @param before the function applied before this
* @return a function composed of before and this
* @throws NullPointerException if before is null
*/
default <V> Function1<V, R> compose(Function<? super V, ? extends T1> before) {
Objects.requireNonNull(before, "before is null");
return v -> apply(before.apply(v));
}
}
interface Function1Module {
// DEV-NOTE: we do not plan to expose this as public API
@SuppressWarnings("unchecked")
static <T extends Throwable, R> R sneakyThrow(Throwable t) throws T {
throw (T) t;
}
}