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Functional Java is an open source library that supports closures for the Java programming language
package fj.function;
import static fj.Function.*;
import fj.F;
import fj.Monoid;
import fj.Semigroup;
import fj.data.List;
import fj.data.Stream;
import static fj.Semigroup.disjunctionSemigroup;
import static fj.Semigroup.conjunctionSemigroup;
import static fj.Semigroup.exclusiveDisjunctionSemiGroup;
/**
* Curried logical functions.
*
* @version %build.number%
*/
public final class Booleans {
private Booleans() {
throw new UnsupportedOperationException();
}
/**
* Curried form of logical "inclusive or" (disjunction).
*/
public static final F> or = disjunctionSemigroup.sum();
/**
* Curried form of logical "and" (conjunction).
*/
public static final F> and = conjunctionSemigroup.sum();
/**
* Curried form of logical xor (nonequivalence).
*/
public static final F> xor = exclusiveDisjunctionSemiGroup.sum();
/**
* Logical negation.
*/
public static final F not = p -> !p;
/**
* Curried form of logical "only if" (material implication).
*/
public static final F> implies = curry((p, q) -> !p || q);
/**
* Curried form of logical "if" (reverse material implication).
*/
public static final F> if_ = flip(implies);
/**
* Curried form of logical "if and only if" (biconditional, equivalence).
*/
public static final F> iff = compose2(not, xor);
/**
* Curried form of logical "not implies" (nonimplication).
*/
public static final F> nimp = compose2(not, implies);
/**
* Curried form of logical "not if" (reverse nonimplication).
*/
public static final F> nif = compose2(not, if_);
/**
* Curried form of logical "not or".
*/
public static final F> nor = compose2(not, or);
/**
* Returns true if all the elements of the given list are true.
*
* @param l A list to check for all the elements being true.
* @return true if all the elements of the given list are true. False otherwise.
*/
public static boolean and(final List l) {
return Monoid.conjunctionMonoid.sumLeft(l);
}
/**
* maps given function to the predicate function
* @param p predicate to be mapped over
* @param f function
* @return predicate function
*/
public static F contramap(F f, F p){
return compose(p, f);
}
/**
* alias for contramap
* @param p predicate to be mapped over
* @param f function
* @return predicate function
*/
public static F is(F f, F p){
return contramap(f, p);
}
/**
* returns inverse of contramap
* @param p predicate to be mapped over
* @param f function
* @return predicate function
*/
public static F isnot(F f, F p){
return compose(not, contramap(f, p));
}
/**
* composes the given predicate using conjunction
* @param p1 first predicate
* @param p2 second predicate
* @return composed predicate function
*/
public static F and(F p1, F p2){
return Semigroup.functionSemigroup(conjunctionSemigroup).sum(p1, p2);
}
/**
* composes the given predicate using exclusive disjunction
* @param p1 first predicate
* @param p2 second predicate
* @return composed predicate function
*/
public static F xor(F p1, F p2){
return Semigroup.functionSemigroup(exclusiveDisjunctionSemiGroup).sum(p1, p2);
}
/**
* returns composed predicate using disjunction
* @param p1 first predicate
* @param p2 second predicate
* @return composed predicate
*/
public static F or(F p1, F p2){
return Semigroup.functionSemigroup(disjunctionSemigroup).sum(p1, p2);
}
/**
* Returns true if all the elements of the given stream are true.
*
* @param l A stream to check for all the elements being true.
* @return true if all the elements of the given stream are true. False otherwise.
*/
public static boolean and(final Stream l) {
return Monoid.conjunctionMonoid.sumLeft(l);
}
/**
* Returns composed predicate
*
* @param l A stream of predicates
* @return composed predicate
*/
public static F andAll(final Stream> l) {
return Monoid.functionMonoid(Monoid.conjunctionMonoid).sumLeft(l);
}
/**
* Returns a composed predicate of given List of predicates
*
* @param l A list of predicate functions
* @return composed predicate function
*/
public static F andAll(final List> l) {
return Monoid.functionMonoid(Monoid.conjunctionMonoid).sumLeft(l);
}
/**
* Returns a composed predicate of given List of predicates
*
* @param l A list of predicate functions
* @return composed predicate function
*/
public static F orAll(final List> l) {
return Monoid.functionMonoid(Monoid.disjunctionMonoid).sumLeft(l);
}
/**
* Returns a composed predicate of given Stream of predicates
*
* @param l A stream of predicate functions
* @return composed predicate function
*/
public static F orAll(final Stream> l) {
return Monoid.functionMonoid(Monoid.disjunctionMonoid).sumLeft(l);
}
/**
* Returns true if any element of the given list is true.
*
* @param l A list to check for any element being true.
* @return true if any element of the given list is true. False otherwise.
*/
public static boolean or(final List l) {
return Monoid.disjunctionMonoid.sumLeft(l);
}
/**
* Returns true if any element of the given stream is true.
*
* @param l A stream to check for any element being true.
* @return true if any element of the given stream is true. False otherwise.
*/
public static boolean or(final Stream l) {
return Monoid.disjunctionMonoid.sumLeft(l);
}
/**
* Negates the given predicate.
*
* @param p A predicate to negate.
* @return The negation of the given predicate.
*/
public static F not(final F p) {
return compose(not, p);
}
/**
* Curried form of conditional. If the first argument is true, returns the second argument,
* otherwise the third argument.
*
* @return A function that returns its second argument if the first argument is true, otherwise the third argument.
*/
public static F>> cond() {
return curry((p, a1, a2) -> p ? a1 : a2);
}
}