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/**           __  __
 *    _____ _/ /_/ /_    Computational Intelligence Library (CIlib)
 *   / ___/ / / / __ \   (c) CIRG @ UP
 *  / /__/ / / / /_/ /   http://cilib.net
 *  \___/_/_/_/_.___/
 */
package net.sourceforge.cilib.util.functions;

import com.google.common.base.Predicate;
import fj.Equal;
import fj.F;
import fj.F2;
import fj.Function;
import fj.Ord;
import fj.Ordering;
import fj.P2;
import fj.data.List;

public final class Utils {
    
    private Utils() {}
    
    public static > F> iterableList() {
        return new F>() {
            @Override
            public List f(I a) {
                return List.iterableList(a);
            }
        };
    }
    
    public static  F, T>> index() {
        return new F, T>>() {
            @Override
            public F, T> f(final Integer a) {
                return new F, T>() {
                    @Override
                    public T f(List b) {
                        return b.index(a);
                    }
                };
            }
        };
    }
    
    public static F precision(final int p) {
        return new F() {
            @Override
            public Double f(Double a) {
                return Math.round(Math.pow(10, p) * a) / Math.pow(10, p);
            }
        };
    }
    
    public static  F2, List, List> pairwise(final F> f) {
        return new F2, List, List>() {
            @Override
            public List f(List a, List b) {
                return a.zip(b).map(new F, A>() {
                    @Override
                    public A f(P2 a) {
                        return f.f(a._1()).f(a._2());
                    }                    
                });
            }
        };
    }
    
    public static  F predicate(final Predicate pred) {
        return new F() {
            @Override
            public Boolean f(T a) {
                return pred.apply(a);
            }
        };
    }
    
    public static  Ord equalOrd() {
        return Ord.ord(Function.curry(new F2() {
            @Override
            public Ordering f(T a, T b) {
                return Ordering.EQ;
            }
        }));
    }
    
    public static  Equal alwaysEqual() {
        return Equal.equal(Function.curry(new F2() {
            @Override
            public Boolean f(T a, T b) {
                return true;
            }
        }));
    }

}