Add EveryNthSequence

Author: pambrose

README.md

@@ -5,10 +5,14 @@ The repo was motivated by [this post](https://medium.com/@desaismital/declarativ
 * [Continuations, Sequences and Yields](src/main/kotlin/org/athenian/ContinuationsSequencesAndYields.kt)
 * [Collection Operations](src/main/kotlin/org/athenian/CollectionOperations.kt)
 * [Chained Operations](src/main/kotlin/org/athenian/ChainedOperations.kt)
-* [Sequnce Ordering](src/main/kotlin/org/athenian/SequenceOrdering.kt)
+* [Sequence Ordering](src/main/kotlin/org/athenian/SequenceOrdering.kt)
 * [Eager vs Lazy Ordering](src/main/kotlin/org/athenian/EvaluationOrdering.kt)
 * [More Eager vs Lazy Ordering](src/main/kotlin/org/athenian/MoreEvaluationOrdering.kt)
 * [Expensive Calculations](src/main/kotlin/org/athenian/ExpensiveCalculations.kt)
 * [Processing Data](src/main/kotlin/org/athenian/LogReader.kt)
+* [Every Other Sequence Action](src/main/kotlin/org/athenian/EveryOtherSequence.kt)
+* [Every Nth Sequence Action](src/main/kotlin/org/athenian/EveryNthSequence.kt)
 
 A good post on Sequences is [here](https://blog.kotlin-academy.com/effective-kotlin-use-sequence-for-bigger-collections-with-more-than-one-processing-step-649a15bb4bf).
+
+A good post on creating Sequence Acitons is [here](https://typealias.com/guides/inside-kotlin-sequences/)

src/main/kotlin/org/athenian/EveryNthSequence.kt

@@ -0,0 +1,29 @@
+package org.athenian
+
+fun <T> Sequence<T>.everyNth(inc: Int) = EveryNthSequence(inc, this)
+
+class EveryNthSequence<T>(private val inc: Int, private val underlyingSequence: Sequence<T>) : Sequence<T> {
+    override fun iterator() =
+        object : Iterator<T> {
+            val iterator = underlyingSequence.iterator()
+
+            override fun hasNext() = iterator.hasNext()
+
+            override fun next(): T {
+                val item = iterator.next()
+                (1..inc - 1).forEach {
+                    if (iterator.hasNext())
+                        iterator.next()
+                }
+                return item
+            }
+        }
+}
+
+fun main() {
+    (0..50)
+        .asSequence()
+        .everyNth(5)
+        .forEach { println("Value: $it") }
+
+}

src/main/kotlin/org/athenian/EveryOtherSequence.kt

@@ -0,0 +1,26 @@
+package org.athenian
+
+fun <T> Sequence<T>.everyOther() = EveryOtherSequence(this)
+
+class EveryOtherSequence<T>(private val underlyingSequence: Sequence<T>) : Sequence<T> {
+    override fun iterator() =
+        object : Iterator<T> {
+            val iterator = underlyingSequence.iterator()
+
+            override fun hasNext() = iterator.hasNext()
+
+            override fun next(): T {
+                val item = iterator.next()
+                if (iterator.hasNext())
+                    iterator.next()
+                return item
+            }
+        }
+}
+
+fun main() {
+    (0..10)
+        .asSequence()
+        .everyOther()
+        .forEach { println("Value: $it") }
+}