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package com.ajjpj.afoundation.collection.immutable;

import com.ajjpj.afoundation.function.*;


/**
 * This interface represents collections that can be traversed "as whole" but not necessarily stepwise. Persistent collections
 *  are typical examples of this: They require cleanup (resource deallocation) after iterating is through, and exporting a
 *  java.util.Iterator can not guarantee that.
 *
 * @author arno
 */
public interface ATraversable extends AMonadicOps {
    /**
     * Executes the statement {@code f} for each element of the {@code ATraversable}.
     */
     void foreach(AStatement1 f) throws E;

    @Override  ATraversable filter(APredicate pred) throws E;
    @Override  ATraversable map(AFunction1 f) throws E;
    @Override  ATraversable flatMap(AFunction1, E> f) throws E;
    @Override  ATraversable collect (APartialFunction pf) throws E;

    /**
     * This method 'folds' the elements of this collection into a single value. It iterates over the elements, passing the
     *  intermediate result and the element to the aggregation function {@code f}. 
     *
     * For example, if this collections holds elements of type Integer, you could compute the sum of all elements by calling
     *  {@code foldLeft (0, (x,y) -> x+y); }.
     *
     * @param startValue initial value that is used to initialize the intermediate result
     * @param f the aggregation function
     * @return the resulting value of the aggregation
     */
     R foldLeft(R startValue, AFunction2 f) throws E;

    @Override  AOption find(APredicate pred) throws E;

    @Override  ATraversable flatten();

    @Override  boolean forAll(APredicate pred) throws E;
    @Override  boolean exists(APredicate pred) throws E;
}