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amarpotghanamarpotghan
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adding predicate combinators
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‎core/src/main/java/fj/function/Booleans.java‎

Lines changed: 96 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,11 @@
11
package fj.function;
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3-
import fj.F;
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import fj.F2;
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import fj.F3;
3+
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import static fj.Function.*;
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6+
import fj.F;
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import fj.Monoid;
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import fj.Semigroup;
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import fj.data.List;
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import fj.data.Stream;
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@@ -42,20 +42,12 @@ private Booleans() {
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/**
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* Logical negation.
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*/
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public static final F<Boolean, Boolean> not = new F<Boolean, Boolean>() {
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public Boolean f(final Boolean p) {
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return !p;
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}
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};
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public static final F<Boolean, Boolean> not = p -> !p;
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/**
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* Curried form of logical "only if" (material implication).
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*/
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public static final F<Boolean, F<Boolean, Boolean>> implies = curry(new F2<Boolean, Boolean, Boolean>() {
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public Boolean f(final Boolean p, final Boolean q) {
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return !p || q;
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}
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});
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public static final F<Boolean, F<Boolean, Boolean>> implies = curry((p, q) -> !p || q);
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/**
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* Curried form of logical "if" (reverse material implication).
@@ -92,6 +84,56 @@ public static boolean and(final List<Boolean> l) {
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return Monoid.conjunctionMonoid.sumLeft(l);
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}
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/**
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* maps function on given predicate function
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* @param p predicate to be mapped over
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* @param f function
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* @return predicate function
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*/
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public static <A, B> F<B, Boolean> contramap(F<B, A> f, F<A, Boolean> p){
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return compose(p, f);
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}
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/**
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* checks if given predicate does not hold for given function
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* @param p predicate to be mapped over
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* @param f function
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* @return predicate function
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*/
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public static <A, B> F<B, Boolean> isnot(F<B, A> f, F<A, Boolean> p){
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return compose(not, contramap(f, p));
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}
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/**
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* composes given predicates using conjunction
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* @param p1 first predicate
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* @param p2 second predicate
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* @return composed predicate function
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*/
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public static <A> F<A, Boolean> and(F<A, Boolean> p1, F<A, Boolean> p2){
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return Semigroup.<A, Boolean>functionSemigroup(conjunctionSemigroup).sum(p1, p2);
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}
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/**
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* composes given predicates using exclusive disjunction
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* @param p1 first predicate
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* @param p2 second predicate
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* @return composed predicate function
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*/
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public static <A> F<A, Boolean> xor(F<A, Boolean> p1, F<A, Boolean> p2){
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return Semigroup.<A, Boolean>functionSemigroup(exclusiveDisjunctionSemiGroup).sum(p1, p2);
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}
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/**
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* returns composes given predicates using disjunction
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* @param p1 first predicate
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* @param p2 second predicate
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* @return composed predicate function
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*/
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public static <A> F<A, Boolean> or(F<A, Boolean> p1, F<A, Boolean> p2){
134+
return Semigroup.<A, Boolean>functionSemigroup(disjunctionSemigroup).sum(p1, p2);
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}
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/**
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* Returns true if all the elements of the given stream are true.
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*
@@ -102,6 +144,46 @@ public static boolean and(final Stream<Boolean> l) {
102144
return Monoid.conjunctionMonoid.sumLeft(l);
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}
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147+
/**
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* Returns a composed predicate of given Stream of predicates
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*
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* @param l A stream of predicate functions
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* @return composed predicate function
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*/
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public static <A> F<A, Boolean> andAll(final Stream<F<A, Boolean>> l) {
154+
return Monoid.<A, Boolean>functionMonoid(Monoid.conjunctionMonoid).sumLeft(l);
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}
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/**
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* Returns a composed predicate of given List of predicates
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*
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* @param l A list of predicate functions
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* @return composed predicate function
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*/
163+
public static <A> F<A, Boolean> andAll(final List<F<A, Boolean>> l) {
164+
return Monoid.<A, Boolean>functionMonoid(Monoid.conjunctionMonoid).sumLeft(l);
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}
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/**
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* Returns a composed predicate of given List of predicates
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*
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* @param l A list of predicate functions
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* @return composed predicate function
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*/
173+
public static <A> F<A, Boolean> orAll(final List<F<A, Boolean>> l) {
174+
return Monoid.<A, Boolean>functionMonoid(Monoid.disjunctionMonoid).sumLeft(l);
175+
}
176+
177+
/**
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* Returns a composed predicate of given Stream of predicates
179+
*
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* @param l A stream of predicate functions
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* @return composed predicate function
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*/
183+
public static <A> F<A, Boolean> orAll(final Stream<F<A, Boolean>> l) {
184+
return Monoid.<A, Boolean>functionMonoid(Monoid.disjunctionMonoid).sumLeft(l);
185+
}
186+
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/**
106188
* Returns true if any element of the given list is true.
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*
@@ -139,10 +221,6 @@ public static <A> F<A, Boolean> not(final F<A, Boolean> p) {
139221
* @return A function that returns its second argument if the first argument is true, otherwise the third argument.
140222
*/
141223
public static <A> F<Boolean, F<A, F<A, A>>> cond() {
142-
return curry(new F3<Boolean, A, A, A>() {
143-
public A f(final Boolean p, final A a1, final A a2) {
144-
return p ? a1 : a2;
145-
}
146-
});
224+
return curry((p, a1, a2) -> p ? a1 : a2);
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}
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}

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