Mercurial > hg > Members > tatsuki > functionaljava-master > core
view src/main/java/fj/Ord.java @ 0:fe80c1edf1be
add getLoop
author | tatsuki |
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date | Fri, 20 Mar 2015 21:04:03 +0900 |
parents | |
children | 8ed7d71e8617 |
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package fj; import fj.data.Array; import fj.data.Either; import fj.data.List; import fj.data.Natural; import fj.data.NonEmptyList; import fj.data.Option; import fj.data.Set; import fj.data.Stream; import fj.data.Validation; import java.math.BigDecimal; import java.math.BigInteger; import static fj.Function.curry; /** * Tests for ordering between two objects. * * @version %build.number% */ public final class Ord<A> { private final F<A, F<A, Ordering>> f; private Ord(final F<A, F<A, Ordering>> f) { this.f = f; } /** * First-class ordering. * * @return A function that returns an ordering for its arguments. */ public F<A, F<A, Ordering>> compare() { return f; } /** * Returns an ordering for the given arguments. * * @param a1 An instance to compare for ordering to another. * @param a2 An instance to compare for ordering to another. * @return An ordering for the given arguments. */ public Ordering compare(final A a1, final A a2) { return f.f(a1).f(a2); } /** * Returns <code>true</code> if the given arguments are equal, <code>false</code> otherwise. * * @param a1 An instance to compare for equality to another. * @param a2 An instance to compare for equality to another. * @return <code>true</code> if the given arguments are equal, <code>false</code> otherwise. */ public boolean eq(final A a1, final A a2) { return compare(a1, a2) == Ordering.EQ; } /** * Returns an <code>Equal</code> for this order. * * @return An <code>Equal</code> for this order. */ public Equal<A> equal() { return Equal.equal(curry(new F2<A, A, Boolean>() { public Boolean f(final A a1, final A a2) { return eq(a1, a2); } })); } /** * Maps the given function across this ord as a contra-variant functor. * * @param f The function to map. * @return A new ord. */ public <B> Ord<B> comap(final F<B, A> f) { return ord(F1Functions.o(F1Functions.o(F1Functions.<B, A, Ordering>andThen(f), this.f), f)); } /** * Returns <code>true</code> if the first given argument is less than the second given argument, * <code>false</code> otherwise. * * @param a1 An instance to compare for ordering to another. * @param a2 An instance to compare for ordering to another. * @return <code>true</code> if the first given argument is less than the second given argument, * <code>false</code> otherwise. */ public boolean isLessThan(final A a1, final A a2) { return compare(a1, a2) == Ordering.LT; } /** * Returns <code>true</code> if the first given argument is greater than the second given * argument, <code>false</code> otherwise. * * @param a1 An instance to compare for ordering to another. * @param a2 An instance to compare for ordering to another. * @return <code>true</code> if the first given argument is greater than the second given * argument, <code>false</code> otherwise. */ public boolean isGreaterThan(final A a1, final A a2) { return compare(a1, a2) == Ordering.GT; } /** * Returns a function that returns true if its argument is less than the argument to this method. * * @param a A value to compare against. * @return A function that returns true if its argument is less than the argument to this method. */ public F<A, Boolean> isLessThan(final A a) { return new F<A, Boolean>() { public Boolean f(final A a2) { return compare(a2, a) == Ordering.LT; } }; } /** * Returns a function that returns true if its argument is greater than than the argument to this method. * * @param a A value to compare against. * @return A function that returns true if its argument is greater than the argument to this method. */ public F<A, Boolean> isGreaterThan(final A a) { return new F<A, Boolean>() { public Boolean f(final A a2) { return compare(a2, a) == Ordering.GT; } }; } /** * Returns the greater of its two arguments. * * @param a1 A value to compare with another. * @param a2 A value to compare with another. * @return The greater of the two values. */ public A max(final A a1, final A a2) { return isGreaterThan(a1, a2) ? a1 : a2; } /** * Returns the lesser of its two arguments. * * @param a1 A value to compare with another. * @param a2 A value to compare with another. * @return The lesser of the two values. */ public A min(final A a1, final A a2) { return isLessThan(a1, a2) ? a1 : a2; } /** * A function that returns the greater of its two arguments. */ public final F<A, F<A, A>> max = curry(new F2<A, A, A>() { public A f(final A a, final A a1) { return max(a, a1); } }); /** * A function that returns the lesser of its two arguments. */ public final F<A, F<A, A>> min = curry(new F2<A, A, A>() { public A f(final A a, final A a1) { return min(a, a1); } }); /** * Returns an order instance that uses the given equality test and ordering function. * * @param f The order function. * @return An order instance. */ public static <A> Ord<A> ord(final F<A, F<A, Ordering>> f) { return new Ord<A>(f); } /** * An order instance for the <code>boolean</code> type. */ public static final Ord<Boolean> booleanOrd = new Ord<Boolean>( new F<Boolean, F<Boolean, Ordering>>() { public F<Boolean, Ordering> f(final Boolean a1) { return new F<Boolean, Ordering>() { public Ordering f(final Boolean a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>byte</code> type. */ public static final Ord<Byte> byteOrd = new Ord<Byte>( new F<Byte, F<Byte, Ordering>>() { public F<Byte, Ordering> f(final Byte a1) { return new F<Byte, Ordering>() { public Ordering f(final Byte a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>char</code> type. */ public static final Ord<Character> charOrd = new Ord<Character>( new F<Character, F<Character, Ordering>>() { public F<Character, Ordering> f(final Character a1) { return new F<Character, Ordering>() { public Ordering f(final Character a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>double</code> type. */ public static final Ord<Double> doubleOrd = new Ord<Double>( new F<Double, F<Double, Ordering>>() { public F<Double, Ordering> f(final Double a1) { return new F<Double, Ordering>() { public Ordering f(final Double a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>float</code> type. */ public static final Ord<Float> floatOrd = new Ord<Float>( new F<Float, F<Float, Ordering>>() { public F<Float, Ordering> f(final Float a1) { return new F<Float, Ordering>() { public Ordering f(final Float a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>int</code> type. */ public static final Ord<Integer> intOrd = new Ord<Integer>( new F<Integer, F<Integer, Ordering>>() { public F<Integer, Ordering> f(final Integer a1) { return new F<Integer, Ordering>() { public Ordering f(final Integer a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>BigInteger</code> type. */ public static final Ord<BigInteger> bigintOrd = new Ord<BigInteger>( new F<BigInteger, F<BigInteger, Ordering>>() { public F<BigInteger, Ordering> f(final BigInteger a1) { return new F<BigInteger, Ordering>() { public Ordering f(final BigInteger a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>BigDecimal</code> type. */ public static final Ord<BigDecimal> bigdecimalOrd = new Ord<BigDecimal>( new F<BigDecimal, F<BigDecimal, Ordering>>() { public F<BigDecimal, Ordering> f(final BigDecimal a1) { return new F<BigDecimal, Ordering>() { public Ordering f(final BigDecimal a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>long</code> type. */ public static final Ord<Long> longOrd = new Ord<Long>( new F<Long, F<Long, Ordering>>() { public F<Long, Ordering> f(final Long a1) { return new F<Long, Ordering>() { public Ordering f(final Long a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the <code>short</code> type. */ public static final Ord<Short> shortOrd = new Ord<Short>( new F<Short, F<Short, Ordering>>() { public F<Short, Ordering> f(final Short a1) { return new F<Short, Ordering>() { public Ordering f(final Short a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the {@link Ordering} type. */ public static final Ord<Ordering> orderingOrd = new Ord<Ordering>(curry(new F2<Ordering, Ordering, Ordering>() { public Ordering f(final Ordering o1, final Ordering o2) { return o1 == o2 ? Ordering.EQ : o1 == Ordering.LT ? Ordering.LT : o2 == Ordering.LT ? Ordering.GT : o1 == Ordering.EQ ? Ordering.LT : Ordering.GT; } })); /** * An order instance for the {@link String} type. */ public static final Ord<String> stringOrd = new Ord<String>( new F<String, F<String, Ordering>>() { public F<String, Ordering> f(final String a1) { return new F<String, Ordering>() { public Ordering f(final String a2) { final int x = a1.compareTo(a2); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); /** * An order instance for the {@link StringBuffer} type. */ public static final Ord<StringBuffer> stringBufferOrd = new Ord<StringBuffer>(new F<StringBuffer, F<StringBuffer, Ordering>>() { public F<StringBuffer, Ordering> f(final StringBuffer a1) { return new F<StringBuffer, Ordering>() { public Ordering f(final StringBuffer a2) { return stringOrd.compare(a1.toString(), a2.toString()); } }; } }); /** * An order instance for the {@link StringBuffer} type. */ public static final Ord<StringBuilder> stringBuilderOrd = new Ord<StringBuilder>(new F<StringBuilder, F<StringBuilder, Ordering>>() { public F<StringBuilder, Ordering> f(final StringBuilder a1) { return new F<StringBuilder, Ordering>() { public Ordering f(final StringBuilder a2) { return stringOrd.compare(a1.toString(), a2.toString()); } }; } }); /** * An order instance for the {@link Option} type. * * @param oa Order across the element of the option. * @return An order instance for the {@link Option} type. */ public static <A> Ord<Option<A>> optionOrd(final Ord<A> oa) { return new Ord<Option<A>>(new F<Option<A>, F<Option<A>, Ordering>>() { public F<Option<A>, Ordering> f(final Option<A> o1) { return new F<Option<A>, Ordering>() { public Ordering f(final Option<A> o2) { return o1.isNone() ? o2.isNone() ? Ordering.EQ : Ordering.LT : o2.isNone() ? Ordering.GT : oa.f.f(o1.some()).f(o2.some()); } }; } }); } /** * An order instance for the {@link Either} type. * * @param oa Order across the left side of {@link Either}. * @param ob Order across the right side of {@link Either}. * @return An order instance for the {@link Either} type. */ public static <A, B> Ord<Either<A, B>> eitherOrd(final Ord<A> oa, final Ord<B> ob) { return new Ord<Either<A, B>>(new F<Either<A, B>, F<Either<A, B>, Ordering>>() { public F<Either<A, B>, Ordering> f(final Either<A, B> e1) { return new F<Either<A, B>, Ordering>() { public Ordering f(final Either<A, B> e2) { return e1.isLeft() ? e2.isLeft() ? oa.f.f(e1.left().value()).f(e2.left().value()) : Ordering.LT : e2.isLeft() ? Ordering.GT : ob.f.f(e1.right().value()).f(e2.right().value()); } }; } }); } /** * An order instance for the {@link Validation} type. * * @param oa Order across the failing side of {@link Validation}. * @param ob Order across the succeeding side of {@link Validation}. * @return An order instance for the {@link Validation} type. */ public static <A, B> Ord<Validation<A, B>> validationOrd(final Ord<A> oa, final Ord<B> ob) { return eitherOrd(oa, ob).comap(Validation.<A, B>either()); } /** * An order instance for the {@link List} type. * * @param oa Order across the elements of the list. * @return An order instance for the {@link List} type. */ public static <A> Ord<List<A>> listOrd(final Ord<A> oa) { return new Ord<List<A>>(new F<List<A>, F<List<A>, Ordering>>() { public F<List<A>, Ordering> f(final List<A> l1) { return new F<List<A>, Ordering>() { public Ordering f(final List<A> l2) { if (l1.isEmpty()) return l2.isEmpty() ? Ordering.EQ : Ordering.LT; else if (l2.isEmpty()) return l1.isEmpty() ? Ordering.EQ : Ordering.GT; else { final Ordering c = oa.compare(l1.head(), l2.head()); return c == Ordering.EQ ? listOrd(oa).f.f(l1.tail()).f(l2.tail()) : c; } } }; } }); } /** * An order instance for the {@link NonEmptyList} type. * * @param oa Order across the elements of the non-empty list. * @return An order instance for the {@link NonEmptyList} type. */ public static <A> Ord<NonEmptyList<A>> nonEmptyListOrd(final Ord<A> oa) { return listOrd(oa).comap(NonEmptyList.<A>toList_()); } /** * An order instance for the {@link Stream} type. * * @param oa Order across the elements of the stream. * @return An order instance for the {@link Stream} type. */ public static <A> Ord<Stream<A>> streamOrd(final Ord<A> oa) { return new Ord<Stream<A>>(new F<Stream<A>, F<Stream<A>, Ordering>>() { public F<Stream<A>, Ordering> f(final Stream<A> s1) { return new F<Stream<A>, Ordering>() { public Ordering f(final Stream<A> s2) { if (s1.isEmpty()) return s2.isEmpty() ? Ordering.EQ : Ordering.LT; else if (s2.isEmpty()) return s1.isEmpty() ? Ordering.EQ : Ordering.GT; else { final Ordering c = oa.compare(s1.head(), s2.head()); return c == Ordering.EQ ? streamOrd(oa).f.f(s1.tail()._1()).f(s2.tail()._1()) : c; } } }; } }); } /** * An order instance for the {@link Array} type. * * @param oa Order across the elements of the array. * @return An order instance for the {@link Array} type. */ public static <A> Ord<Array<A>> arrayOrd(final Ord<A> oa) { return new Ord<Array<A>>(new F<Array<A>, F<Array<A>, Ordering>>() { public F<Array<A>, Ordering> f(final Array<A> a1) { return new F<Array<A>, Ordering>() { public Ordering f(final Array<A> a2) { int i = 0; //noinspection ForLoopWithMissingComponent for (; i < a1.length() && i < a2.length(); i++) { final Ordering c = oa.compare(a1.get(i), a2.get(i)); if (c == Ordering.GT || c == Ordering.LT) return c; } return i == a1.length() ? i == a2.length() ? Ordering.EQ : Ordering.LT : i == a1.length() ? Ordering.EQ : Ordering.GT; } }; } }); } /** * An order instance for the {@link Set} type. * * @param oa Order across the elements of the set. * @return An order instance for the {@link Set} type. */ public static <A> Ord<Set<A>> setOrd(final Ord<A> oa) { return streamOrd(oa).comap(new F<Set<A>, Stream<A>>() { public Stream<A> f(final Set<A> as) { return as.toStream(); } }); } /** * An order instance for the {@link Unit} type. */ public static final Ord<Unit> unitOrd = ord(curry(new F2<Unit, Unit, Ordering>() { public Ordering f(final Unit u1, final Unit u2) { return Ordering.EQ; } })); /** * An order instance for a product-1. * * @param oa Order across the produced type. * @return An order instance for a product-1. */ public static <A> Ord<P1<A>> p1Ord(final Ord<A> oa) { return oa.comap(P1.<A>__1()); } /** * An order instance for a product-2, with the first factor considered most significant. * * @param oa An order instance for the first factor. * @param ob An order instance for the second factor. * @return An order instance for a product-2, with the first factor considered most significant. */ public static <A, B> Ord<P2<A, B>> p2Ord(final Ord<A> oa, final Ord<B> ob) { return ord(curry(new F2<P2<A, B>, P2<A, B>, Ordering>() { public Ordering f(final P2<A, B> a, final P2<A, B> b) { return oa.eq(a._1(), b._1()) ? ob.compare(a._2(), b._2()) : oa.compare(a._1(), b._1()); } })); } /** * An order instance for a product-3, with the first factor considered most significant. * * @param oa An order instance for the first factor. * @param ob An order instance for the second factor. * @param oc An order instance for the third factor. * @return An order instance for a product-3, with the first factor considered most significant. */ public static <A, B, C> Ord<P3<A, B, C>> p3Ord(final Ord<A> oa, final Ord<B> ob, final Ord<C> oc) { return ord(curry(new F2<P3<A, B, C>, P3<A, B, C>, Ordering>() { public Ordering f(final P3<A, B, C> a, final P3<A, B, C> b) { return oa.eq(a._1(), b._1()) ? p2Ord(ob, oc).compare(P.p(a._2(), a._3()), P.p(b._2(), b._3())) : oa.compare(a._1(), b._1()); } })); } /** * An order instance for the <code>Natural</code> type. */ public static final Ord<Natural> naturalOrd = bigintOrd.comap(Natural.bigIntegerValue); /** * An order instance for the <code>Comparable</code> interface. * * @return An order instance for the <code>Comparable</code> interface. */ public static <A extends Comparable<A>> Ord<A> comparableOrd() { return ord(new F<A, F<A, Ordering>>() { public F<A, Ordering> f(final A a1) { return new F<A, Ordering>() { public Ordering f(final A a2) { return Ordering.fromInt(a1.compareTo(a2)); } }; } }); } /** * An order instance that uses {@link Object#hashCode()} for computing the order and equality, * thus objects returning the same hashCode are considered to be equals (check {@link #hashEqualsOrd()} * for an additional check on {@link Object#equals(Object)}). * * @return An order instance that is based on {@link Object#hashCode()}. * @see #hashEqualsOrd() */ public static <A> Ord<A> hashOrd() { return Ord.<A> ord(new F<A, F<A, Ordering>>() { @Override public F<A, Ordering> f(final A a) { return new F<A, Ordering>() { @Override public Ordering f(final A a2) { final int x = a.hashCode() - a2.hashCode(); return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT; } }; } }); } /** * An order instance that uses {@link Object#hashCode()} and {@link Object#equals} for computing * the order and equality. First the hashCode is compared, if this is equal, objects are compared * using {@link Object#equals}. * * @return An order instance that is based on {@link Object#hashCode()} and {@link Object#equals}. */ public static <A> Ord<A> hashEqualsOrd() { return Ord.<A> ord(new F<A, F<A, Ordering>>() { @Override public F<A, Ordering> f(final A a) { return new F<A, Ordering>() { @Override public Ordering f(final A a2) { final int x = a.hashCode() - a2.hashCode(); return x < 0 ? Ordering.LT : x == 0 && a.equals(a2) ? Ordering.EQ : Ordering.GT; } }; } }); } }