fj.Ord Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of functionaljava Show documentation
Show all versions of functionaljava Show documentation
Functional Java is an open source library that supports closures for the Java programming language
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 java.util.Comparator;
import static fj.Function.curry;
/**
* Tests for ordering between two objects.
*
* @version %build.number%
*/
public final class Ord {
private final F> f;
private Ord(final F> f) {
this.f = f;
}
/**
* First-class ordering.
*
* @return A function that returns an ordering for its arguments.
*/
public F> 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 true if the given arguments are equal, false otherwise.
*
* @param a1 An instance to compare for equality to another.
* @param a2 An instance to compare for equality to another.
* @return true if the given arguments are equal, false otherwise.
*/
public boolean eq(final A a1, final A a2) {
return compare(a1, a2) == Ordering.EQ;
}
/**
* Returns an Equal for this order.
*
* @return An Equal for this order.
*/
public Equal equal() {
return Equal.equal(curry(this::eq));
}
/**
* Maps the given function across this ord as a contra-variant functor.
*
* @param f The function to map.
* @return A new ord.
*/
public Ord contramap(final F f) {
return ord(F1Functions.o(F1Functions.o(F1Functions.andThen(f), this.f), f));
}
/**
* Returns true if the first given argument is less than the second given argument,
* false otherwise.
*
* @param a1 An instance to compare for ordering to another.
* @param a2 An instance to compare for ordering to another.
* @return true if the first given argument is less than the second given argument,
* false otherwise.
*/
public boolean isLessThan(final A a1, final A a2) {
return compare(a1, a2) == Ordering.LT;
}
/**
* Returns true if the first given argument is greater than the second given
* argument, false otherwise.
*
* @param a1 An instance to compare for ordering to another.
* @param a2 An instance to compare for ordering to another.
* @return true if the first given argument is greater than the second given
* argument, false 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 isLessThan(final A a) {
return a2 -> 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 isGreaterThan(final A a) {
return a2 -> 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> max = curry((a, a1) -> max(a, a1));
/**
* A function that returns the lesser of its two arguments.
*/
public final F> min = curry((a, a1) -> min(a, a1));
public final Ord reverse() { return ord(Function.flip(f)); }
/**
* Returns an order instance that uses the given equality test and ordering function.
*
* @param f The order function.
* @return An order instance.
*/
public static Ord ord(final F> f) {
return new Ord(f);
}
/**
* An order instance for the boolean type.
*/
public static final Ord booleanOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the byte type.
*/
public static final Ord byteOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the char type.
*/
public static final Ord charOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the double type.
*/
public static final Ord doubleOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the float type.
*/
public static final Ord floatOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the int type.
*/
public static final Ord intOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the BigInteger type.
*/
public static final Ord bigintOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the BigDecimal type.
*/
public static final Ord bigdecimalOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the long type.
*/
public static final Ord longOrd = ord(
a1 -> a2 -> {
final int x = a1.compareTo(a2);
return x < 0 ? Ordering.LT : x == 0 ? Ordering.EQ : Ordering.GT;
});
/**
* An order instance for the short type.
*/
public static final Ord shortOrd = ord(
a1 -> 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 orderingOrd = Ord.ord(curry((o1, o2) -> 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 stringOrd = ord(
a1 -> 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 stringBufferOrd =
ord(a1 -> a2 -> stringOrd.compare(a1.toString(), a2.toString()));
/**
* An order instance for the {@link StringBuffer} type.
*/
public static final Ord stringBuilderOrd =
ord(a1 -> a2 -> 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 Ord> optionOrd(final Ord oa) {
return ord(o1 -> o2 -> 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 Ord> eitherOrd(final Ord oa, final Ord ob) {
return ord(e1 -> e2 -> 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 Ord> validationOrd(final Ord oa, final Ord ob) {
return eitherOrd(oa, ob).contramap(Validation.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 Ord> listOrd(final Ord oa) {
return ord(l1 -> l2 -> {
List x1 = l1;
List x2 = l2;
while (x1.isNotEmpty() && x2.isNotEmpty()) {
final Ordering o = oa.compare(x1.head(), x2.head());
if (o == Ordering.LT || o == Ordering.GT) {
return o;
}
x1 = x1.tail();
x2 = x2.tail();
}
if (x1.isEmpty() && x2.isEmpty()) {
return Ordering.EQ;
} else if (x1.isEmpty()) {
return Ordering.LT;
} else {
return Ordering.GT;
}
});
}
/**
* 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 Ord> nonEmptyListOrd(final Ord oa) {
return listOrd(oa).contramap(NonEmptyList.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 Ord> streamOrd(final Ord oa) {
return ord(s1 -> 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 Ord> arrayOrd(final Ord oa) {
return ord(a1 -> 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 Ord> setOrd(final Ord oa) {
return streamOrd(oa).contramap(as -> as.toStream());
}
/**
* An order instance for the {@link Unit} type.
*/
public static final Ord unitOrd = ord(curry((Unit u1, Unit u2) -> 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 Ord> p1Ord(final Ord oa) {
return oa.contramap(P1.__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 Ord> p2Ord(final Ord oa, final Ord ob) {
return ord(curry((P2 a, P2 b) -> 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 Ord> p3Ord(final Ord oa, final Ord ob, final Ord oc) {
return ord(curry((P3 a, P3 b) -> 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 Natural type.
*/
public static final Ord naturalOrd = bigintOrd.contramap(Natural.bigIntegerValue);
/**
* An order instance for the Comparable interface.
*
* @return An order instance for the Comparable interface.
*/
public static > Ord comparableOrd() {
return ord(a1 -> a2 -> 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 Ord hashOrd() {
return ord(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 Ord hashEqualsOrd() {
return ord(a -> a2 -> {
final int x = a.hashCode() - a2.hashCode();
return x < 0 ? Ordering.LT : x == 0 && a.equals(a2) ? Ordering.EQ : Ordering.GT;
});
}
class OrdComparator implements Comparator {
@Override
public int compare(A o1, A o2) {
return Ord.this.compare(o1, o2).toInt();
}
}
public Comparator toComparator() {
return new OrdComparator();
}
}