c

src/main/kotlin/blitz/collections/ListOps.kt

@@ -30,4 +30,40 @@ fun <T> MutableList<T>.addFront(value: T) =
     add(0, value)
 
 fun <T: Any> Iterable<T?>.countNotNull() =
-    count { it != null }
+    count { it != null }
+
+fun <T> Iterable<Iterable<T>>.intersections(dest: MutableList<T> = mutableListOf()): MutableList<T> =
+    reduce { acc, li -> acc.intersect(li) }
+        .forEach { dest += it }
+        .let { dest }
+
+fun <T> Iterable<T>.removeAtIndexes(idc: Iterable<Int>, dest: MutableList<T> = mutableListOf()): MutableList<T> =
+    filterIndexedTo(dest) { index, _ -> index !in idc }
+
+fun <T> List<T>.gather(idc: Iterable<Int>): MutableList<T> {
+    val dest = mutableListOf<T>()
+    idc.forEach {
+        dest += get(it)
+    }
+    return dest
+}
+
+fun <T> List<T>.before(idx: Int): List<T> =
+    take(idx)
+
+fun <T> List<T>.after(idx: Int): List<T> =
+    drop(idx + 1)
+
+inline fun <I, reified O> Collection<I>.mapToArray(fn: (I) -> O): Array<O> {
+    val iter = this.iterator()
+    return Array(this.size) {
+        fn(iter.next())
+    }
+}
+
+inline fun <I, reified O> Collection<I>.mapIndexedToArray(fn: (Int, I) -> O): Array<O> {
+    val iter = this.iterator()
+    return Array(this.size) {
+        fn(it, iter.next())
+    }
+}