at.gridtec.lambda4j.function.bi.to.ToDoubleBiFunction2.java Source code

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/*
 * Copyright (c) 2016 Gridtec. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package at.gridtec.lambda4j.function.bi.to;

import at.gridtec.lambda4j.Lambda;
import at.gridtec.lambda4j.consumer.bi.BiConsumer2;
import at.gridtec.lambda4j.function.bi.BiFunction2;
import at.gridtec.lambda4j.function.conversion.DoubleToByteFunction;
import at.gridtec.lambda4j.function.conversion.DoubleToCharFunction;
import at.gridtec.lambda4j.function.conversion.DoubleToFloatFunction;
import at.gridtec.lambda4j.function.conversion.DoubleToShortFunction;
import at.gridtec.lambda4j.function.to.ToDoubleFunction2;
import at.gridtec.lambda4j.predicate.bi.BiPredicate2;

import org.apache.commons.lang3.tuple.Pair;

import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.DoubleConsumer;
import java.util.function.DoubleFunction;
import java.util.function.DoublePredicate;
import java.util.function.DoubleToIntFunction;
import java.util.function.DoubleToLongFunction;
import java.util.function.DoubleUnaryOperator;
import java.util.function.Function;
import java.util.function.ToDoubleBiFunction;
import java.util.function.ToDoubleFunction;

/**
 * Represents an operation that accepts two input arguments and produces a
 * {@code double}-valued result.
 * This is a primitive specialization of {@link BiFunction2}.
 * <p>
 * This is a {@link FunctionalInterface} whose functional method is {@link #applyAsDouble(Object, Object)}.
 *
 * @param <T> The type of the first argument to the function
 * @param <U> The type of the second argument to the function
 * @apiNote This is a JDK lambda.
 * @see BiFunction2
 */
@SuppressWarnings("unused")
@FunctionalInterface
public interface ToDoubleBiFunction2<T, U> extends Lambda, ToDoubleBiFunction<T, U> {

    /**
     * Constructs a {@link ToDoubleBiFunction2} based on a lambda expression or a method reference. Thereby the given
     * lambda expression or method reference is returned on an as-is basis to implicitly transform it to the desired
     * type. With this method, it is possible to ensure that correct type is used from lambda expression or method
     * reference.
     *
     * @param <T> The type of the first argument to the function
     * @param <U> The type of the second argument to the function
     * @param expression A lambda expression or (typically) a method reference, e.g. {@code this::method}
     * @return A {@code ToDoubleBiFunction2} from given lambda expression or method reference.
     * @implNote This implementation allows the given argument to be {@code null}, but only if {@code null} given,
     * {@code null} will be returned.
     * @see <a href="https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html#syntax">Lambda
     * Expression</a>
     * @see <a href="https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html">Method Reference</a>
     */
    static <T, U> ToDoubleBiFunction2<T, U> of(@Nullable final ToDoubleBiFunction2<T, U> expression) {
        return expression;
    }

    /**
     * Calls the given {@link ToDoubleBiFunction} with the given arguments and returns its result.
     *
     * @param <T> The type of the first argument to the function
     * @param <U> The type of the second argument to the function
     * @param function The function to be called
     * @param t The first argument to the function
     * @param u The second argument to the function
     * @return The result from the given {@code ToDoubleBiFunction2}.
     * @throws NullPointerException If given argument is {@code null}
     */
    static <T, U> double call(@Nonnull final ToDoubleBiFunction<? super T, ? super U> function, T t, U u) {
        Objects.requireNonNull(function);
        return function.applyAsDouble(t, u);
    }

    /**
     * Creates a {@link ToDoubleBiFunction2} which uses the {@code first} parameter of this one as argument for the
     * given {@link ToDoubleFunction}.
     *
     * @param <T> The type of the first argument to the function
     * @param <U> The type of the second argument to the function
     * @param function The function which accepts the {@code first} parameter of this one
     * @return Creates a {@code ToDoubleBiFunction2} which uses the {@code first} parameter of this one as argument for
     * the given {@code ToDoubleFunction}.
     * @throws NullPointerException If given argument is {@code null}
     */
    @Nonnull
    static <T, U> ToDoubleBiFunction2<T, U> onlyFirst(@Nonnull final ToDoubleFunction<? super T> function) {
        Objects.requireNonNull(function);
        return (t, u) -> function.applyAsDouble(t);
    }

    /**
     * Creates a {@link ToDoubleBiFunction2} which uses the {@code second} parameter of this one as argument for the
     * given {@link ToDoubleFunction}.
     *
     * @param <T> The type of the first argument to the function
     * @param <U> The type of the second argument to the function
     * @param function The function which accepts the {@code second} parameter of this one
     * @return Creates a {@code ToDoubleBiFunction2} which uses the {@code second} parameter of this one as argument for
     * the given {@code ToDoubleFunction}.
     * @throws NullPointerException If given argument is {@code null}
     */
    @Nonnull
    static <T, U> ToDoubleBiFunction2<T, U> onlySecond(@Nonnull final ToDoubleFunction<? super U> function) {
        Objects.requireNonNull(function);
        return (t, u) -> function.applyAsDouble(u);
    }

    /**
     * Creates a {@link ToDoubleBiFunction2} which always returns a given value.
     *
     * @param <T> The type of the first argument to the function
     * @param <U> The type of the second argument to the function
     * @param ret The return value for the constant
     * @return A {@code ToDoubleBiFunction2} which always returns a given value.
     */
    @Nonnull
    static <T, U> ToDoubleBiFunction2<T, U> constant(double ret) {
        return (t, u) -> ret;
    }

    /**
     * Applies this function to the given arguments.
     *
     * @param t The first argument to the function
     * @param u The second argument to the function
     * @return The return value from the function, which is its result.
     */
    double applyAsDouble(T t, U u);

    /**
     * Applies this function to the given tuple.
     *
     * @param tuple The tuple to be applied to the function
     * @return The return value from the function, which is its result.
     * @throws NullPointerException If given argument is {@code null}
     * @see org.apache.commons.lang3.tuple.Pair
     */
    default double applyAsDouble(@Nonnull Pair<T, U> tuple) {
        Objects.requireNonNull(tuple);
        return applyAsDouble(tuple.getLeft(), tuple.getRight());
    }

    /**
     * Applies this function partially to some arguments of this one, producing a {@link ToDoubleFunction2} as result.
     *
     * @param t The first argument to this function used to partially apply this function
     * @return A {@code ToDoubleFunction2} that represents this function partially applied the some arguments.
     */
    @Nonnull
    default ToDoubleFunction2<U> papplyAsDouble(T t) {
        return (u) -> this.applyAsDouble(t, u);
    }

    /**
     * Returns the number of arguments for this function.
     *
     * @return The number of arguments for this function.
     * @implSpec The default implementation always returns {@code 2}.
     */
    @Nonnegative
    default int arity() {
        return 2;
    }

    /**
     * Returns a composed {@link ToDoubleBiFunction2} that first applies the {@code before} functions to its input, and
     * then applies this function to the result.
     * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation.
     *
     * @param <A> The type of the argument to the first given function, and of composed function
     * @param <B> The type of the argument to the second given function, and of composed function
     * @param before1 The first function to apply before this function is applied
     * @param before2 The second function to apply before this function is applied
     * @return A composed {@code ToDoubleBiFunction2} that first applies the {@code before} functions to its input, and
     * then applies this function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is able to handle every type.
     */
    @Nonnull
    default <A, B> ToDoubleBiFunction2<A, B> compose(@Nonnull final Function<? super A, ? extends T> before1,
            @Nonnull final Function<? super B, ? extends U> before2) {
        Objects.requireNonNull(before1);
        Objects.requireNonNull(before2);
        return (a, b) -> applyAsDouble(before1.apply(a), before2.apply(b));
    }

    /**
     * Returns a composed {@link BiFunction2} that first applies this function to its input, and then applies the
     * {@code after} function to the result.
     * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation.
     *
     * @param <S> The type of return value from the {@code after} function, and of the composed function
     * @param after The function to apply after this function is applied
     * @return A composed {@code BiFunction2} that first applies this function to its input, and then applies the {@code
     * after} function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is able to return every type.
     */
    @Nonnull
    default <S> BiFunction2<T, U, S> andThen(@Nonnull final DoubleFunction<? extends S> after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.apply(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link BiPredicate2} that first applies this function to its input, and then applies the
     * {@code after} predicate to the result. If evaluation of either operation throws an exception, it is relayed to
     * the caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code boolean}.
     *
     * @param after The predicate to apply after this function is applied
     * @return A composed {@code BiPredicate2} that first applies this function to its input, and then applies the
     * {@code after} predicate to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * boolean}.
     */
    @Nonnull
    default BiPredicate2<T, U> andThenToBoolean(@Nonnull final DoublePredicate after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.test(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link ToByteBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result. If evaluation of either operation throws an exception, it is relayed to the
     * caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code byte}.
     *
     * @param after The function to apply after this function is applied
     * @return A composed {@code ToByteBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * byte}.
     */
    @Nonnull
    default ToByteBiFunction<T, U> andThenToByte(@Nonnull final DoubleToByteFunction after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.applyAsByte(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link ToCharBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result. If evaluation of either operation throws an exception, it is relayed to the
     * caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code char}.
     *
     * @param after The function to apply after this function is applied
     * @return A composed {@code ToCharBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * char}.
     */
    @Nonnull
    default ToCharBiFunction<T, U> andThenToChar(@Nonnull final DoubleToCharFunction after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.applyAsChar(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link ToDoubleBiFunction2} that first applies this function to its input, and then applies
     * the {@code after} operator to the result. If evaluation of either operation throws an exception, it is relayed to
     * the caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code double}.
     *
     * @param after The operator to apply after this function is applied
     * @return A composed {@code ToDoubleBiFunction2} that first applies this function to its input, and then applies
     * the {@code after} operator to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * double}.
     */
    @Nonnull
    default ToDoubleBiFunction2<T, U> andThenToDouble(@Nonnull final DoubleUnaryOperator after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.applyAsDouble(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link ToFloatBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result. If evaluation of either operation throws an exception, it is relayed to the
     * caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code float}.
     *
     * @param after The function to apply after this function is applied
     * @return A composed {@code ToFloatBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * float}.
     */
    @Nonnull
    default ToFloatBiFunction<T, U> andThenToFloat(@Nonnull final DoubleToFloatFunction after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.applyAsFloat(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link ToIntBiFunction2} that first applies this function to its input, and then applies the
     * {@code after} function to the result. If evaluation of either operation throws an exception, it is relayed to the
     * caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code int}.
     *
     * @param after The function to apply after this function is applied
     * @return A composed {@code ToIntBiFunction2} that first applies this function to its input, and then applies the
     * {@code after} function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * int}.
     */
    @Nonnull
    default ToIntBiFunction2<T, U> andThenToInt(@Nonnull final DoubleToIntFunction after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.applyAsInt(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link ToLongBiFunction2} that first applies this function to its input, and then applies the
     * {@code after} function to the result. If evaluation of either operation throws an exception, it is relayed to the
     * caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code long}.
     *
     * @param after The function to apply after this function is applied
     * @return A composed {@code ToLongBiFunction2} that first applies this function to its input, and then applies the
     * {@code after} function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * long}.
     */
    @Nonnull
    default ToLongBiFunction2<T, U> andThenToLong(@Nonnull final DoubleToLongFunction after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.applyAsLong(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link ToShortBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result. If evaluation of either operation throws an exception, it is relayed to the
     * caller of the composed operation. This method is just convenience, to provide the ability to transform this
     * primitive function to an operation returning {@code short}.
     *
     * @param after The function to apply after this function is applied
     * @return A composed {@code ToShortBiFunction} that first applies this function to its input, and then applies the
     * {@code after} function to the result.
     * @throws NullPointerException If given argument is {@code null}
     * @implSpec The input argument of this method is a able to return primitive values. In this case this is {@code
     * short}.
     */
    @Nonnull
    default ToShortBiFunction<T, U> andThenToShort(@Nonnull final DoubleToShortFunction after) {
        Objects.requireNonNull(after);
        return (t, u) -> after.applyAsShort(applyAsDouble(t, u));
    }

    /**
     * Returns a composed {@link BiConsumer2} that fist applies this function to its input, and then consumes the result
     * using the given {@link DoubleConsumer}.
     * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation.
     *
     * @param consumer The operation which consumes the result from this operation
     * @return A composed {@code BiConsumer2} that first applies this function to its input, and then consumes the
     * result using the given {@code DoubleConsumer}.
     * @throws NullPointerException If given argument is {@code null}
     */
    @Nonnull
    default BiConsumer2<T, U> consume(@Nonnull final DoubleConsumer consumer) {
        Objects.requireNonNull(consumer);
        return (t, u) -> consumer.accept(applyAsDouble(t, u));
    }

    /**
     * Returns a tupled version of this function.
     *
     * @return A tupled version of this function.
     */
    @Nonnull
    default ToDoubleFunction2<Pair<T, U>> tupled() {
        return this::applyAsDouble;
    }

    /**
     * Returns a reversed version of this function. This may be useful in recursive context.
     *
     * @return A reversed version of this function.
     */
    @Nonnull
    default ToDoubleBiFunction2<U, T> reversed() {
        return (u, t) -> applyAsDouble(t, u);
    }

    /**
     * Returns a memoized (caching) version of this {@link ToDoubleBiFunction2}. Whenever it is called, the mapping
     * between the input parameters and the return value is preserved in a cache, making subsequent calls returning the
     * memoized value instead of computing the return value again.
     * <p>
     * Unless the function and therefore the used cache will be garbage-collected, it will keep all memoized values
     * forever.
     *
     * @return A memoized (caching) version of this {@code ToDoubleBiFunction2}.
     * @implSpec This implementation does not allow the input parameters or return value to be {@code null} for the
     * resulting memoized function, as the cache used internally does not permit {@code null} keys or values.
     * @implNote The returned memoized function can be safely used concurrently from multiple threads which makes it
     * thread-safe.
     */
    @Nonnull
    default ToDoubleBiFunction2<T, U> memoized() {
        if (isMemoized()) {
            return this;
        } else {
            final Map<Pair<T, U>, Double> cache = new ConcurrentHashMap<>();
            final Object lock = new Object();
            return (ToDoubleBiFunction2<T, U> & Memoized) (t, u) -> {
                final double returnValue;
                synchronized (lock) {
                    returnValue = cache.computeIfAbsent(Pair.of(t, u),
                            key -> applyAsDouble(key.getLeft(), key.getRight()));
                }
                return returnValue;
            };
        }
    }

    /**
     * Returns a composed {@link BiFunction2} which represents this {@link ToDoubleBiFunction2}. Thereby the primitive
     * input argument for this function is autoboxed. This method provides the possibility to use this
     * {@code ToDoubleBiFunction2} with methods provided by the {@code JDK}.
     *
     * @return A composed {@code BiFunction2} which represents this {@code ToDoubleBiFunction2}.
     */
    @Nonnull
    default BiFunction2<T, U, Double> boxed() {
        return this::applyAsDouble;
    }

}