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mperrymperry
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Merge branch 'scans' of https://github.com/pbzdyl/functionaljava into pbzdyl-scans
2 parents 520f412 + 9bbdf22 commit 830e22a

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‎core/src/main/java/fj/data/Array.java‎

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@@ -291,6 +291,144 @@ public <B> B foldLeft(final F2<B, A, B> f, final B b) {
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return foldLeft(curry(f), b);
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}
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/**
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* Performs a fold left accummulating and returns an array of the intermediate results.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (initial value/previous result and next array element)
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* @param b The beginning value to start the application from.
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* @return The array containing all intermediate results of the left-fold reduction.
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*/
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@SuppressWarnings({"unchecked"})
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public <B> Array<B> scanLeft(final F<B, F<A, B>> f, final B b) {
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final Object[] bs = new Object[a.length];
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B x = b;
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for (int i = 0; i < a.length; i++) {
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x = f.f(x).f((A) a[i]);
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bs[i] = x;
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}
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return new Array<B>(bs);
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}
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/**
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* Performs a left-fold accummulating and returns an array of the intermediate results.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (initial value/previous result and next array element)
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* @param b The beginning value to start the application from.
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* @return The array containing all intermediate results of the left-fold reduction.
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*/
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public <B> Array<B> scanLeft(final F2<B, A, B> f, final B b) {
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return scanLeft(curry(f), b);
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}
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/**
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* Performs a left-fold accummulating using first array element as a starting value
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* and returns an array of the intermediate results.
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* It will fail for empty arrays.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (next array element and first array element/previous result)
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* @return The array containing all intermediate results of the left-fold reduction.
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*/
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@SuppressWarnings({"unchecked"})
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public Array<A> scanLeft1(final F<A, F<A, A>> f) {
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final Object[] bs = new Object[a.length];
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A x = get(0);
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bs[0] = x;
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for (int i = 1; i < a.length; i++) {
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x = f.f(x).f((A) a[i]);
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bs[i] = x;
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}
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return new Array<A>(bs);
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}
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/**
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* Performs a left-fold accummulating using first array element as a starting value
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* and returns an array of the intermediate results.
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* It will fail for empty arrays.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (next array element and first array element/previous result)
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* @return The array containing all intermediate results of the left-fold reduction.
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*/
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public Array<A> scanLeft1(final F2<A, A, A> f) {
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return scanLeft1(curry(f));
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}
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/**
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* Performs a right-fold accummulating and returns an array of the intermediate results.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (previous array element and initial value/previous result)
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* @param b The beginning value to start the application from.
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* @return The array containing all intermediate results of the right-fold reduction.
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*/
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@SuppressWarnings({"unchecked"})
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public <B> Array<B> scanRight(final F<A, F<B, B>>f, final B b) {
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final Object[] bs = new Object[a.length];
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B x = b;
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for (int i = a.length - 1; i >= 0; i--) {
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x = f.f((A) a[i]).f(x);
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bs[i] = x;
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}
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return new Array<B>(bs);
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}
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/**
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* Performs a right-fold accummulating and returns an array of the intermediate results.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (previous array element and initial value/previous result)
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* @param b The beginning value to start the application from.
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* @return The array containing all intermediate results of the right-fold reduction.
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*/
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public <B> Array<B> scanRight(final F2<A, B, B> f, final B b) {
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return scanRight(curry(f), b);
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}
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/**
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* Performs a right-fold accummulating using last array element as a starting value
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* and returns an array of the intermediate results.
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* It will fail for empty arrays.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (previous array element and last array element/previous result)
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* @return The array containing all intermediate results of the right-fold reduction.
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*/
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@SuppressWarnings({"unchecked"})
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public Array<A> scanRight1(final F<A, F<A, A>>f) {
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final Object[] bs = new Object[a.length];
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A x = get(length() - 1);
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bs[length() - 1] = x;
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for (int i = a.length - 2; i >= 0; i--) {
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x = f.f((A) a[i]).f(x);
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bs[i] = x;
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}
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return new Array<A>(bs);
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}
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/**
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* Performs a right-fold accummulating using last array element as a starting value
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* and returns an array of the intermediate results.
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* It will fail for empty arrays.
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* This function runs in constant stack space.
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*
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* @param f The function to apply on each argument pair (previous array element and last array element/previous result)
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* @return The array containing all intermediate results of the right-fold reduction.
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*/
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public Array<A> scanRight1(final F2<A, A, A> f) {
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return scanRight1(curry(f));
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}
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/**
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* Binds the given function across each element of this array with a final join.
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*

‎tests/src/test/scala/fj/data/CheckArray.scala‎

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Original file line numberDiff line numberDiff line change
@@ -62,6 +62,23 @@ object CheckArray extends Properties("Array") {
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a.foldLeft(((a: Array[String], b: String) => array[String](scala.Array(b): _*).append(a)), empty[String]),
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a.reverse.foldRight((a: String, b: Array[String]) => array[String](scala.Array(a): _*).append(b), empty[String])))
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property("scans") = forAll((a: Array[Int], z: Int) => {
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val add = (x: Int, y: Int) => x + y
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val left = a.scanLeft(add, z)
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val right = a.reverse().scanRight(add, z).reverse()
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arrayEqual(Equal.anyEqual[Int]).eq(left, right)
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})
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property("scans1") = forAll((a: Array[Int]) =>
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(a.length() > 0) ==> {
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val add = (x: Int, y: Int) => x + y
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val left = a.scanLeft1(add)
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val right = a.reverse().scanRight1(add).reverse()
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arrayEqual(Equal.anyEqual[Int]).eq(left, right)
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})
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property("bindLeftIdentity") = forAll((a: Array[String], s: String) => {
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def f(s: String) = array[String](scala.Array(s.reverse): _*)
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arrayEqual(stringEqual).eq(

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