You can do this pretty straightforwardly with an implicit class and a for-comprehension in Scala 2.10: implicit class Crossable[X](xs: Traversable[X]) { def cross[Y](ys: Traversable[Y]) = for { x <- xs; y <- ys } yield (x, y) } val xs = Seq(1, 2) val ys = List(“hello”, “world”, “bye”) And now: scala> xs cross ys … Read more
In a pure functional language, you can’t do anything that has a side effect. A side effect would mean that evaluating an expression changes some internal state that would later cause evaluating the same expression to have a different result. In a pure functional language you can evaluate the same expression as often as you … Read more
The key is that x :: somelist does not mutate somelist, but instead creates a new list, which contains x followed by all elements of somelist. This can be done in O(1) time because you only need to set somelist as the successor of x in the newly created, singly linked list. If doubly linked … Read more
Java 8 (released March 18th 2014) does support currying. The example Java code posted in the answer by missingfaktor can be rewritten as: import java.util.function.*; import static java.lang.System.out; // Tested with JDK 1.8.0-ea-b75 public class CurryingAndPartialFunctionApplication { public static void main(String[] args) { IntBinaryOperator simpleAdd = (a, b) -> a + b; IntFunction<IntUnaryOperator> curriedAdd = … Read more
scala> (List(1,2,3),List(4,5,6),List(7,8,9)).zipped.toList res0: List[(Int, Int, Int)] = List((1,4,7), (2,5,8), (3,6,9)) For future reference.
rows.sortBy(r => (r.lastName, r.firstName))
The other uses I’ve found for it besides + and * were with and and or, but now we have any and all to replace those cases. foldl and foldr do come up in Scheme a lot… Here’s some cute usages: Flatten a list Goal: turn [[1, 2, 3], [4, 5], [6, 7, 8]] into … Read more
In the 2009-2012 period, the following things have happened: 2012: From 2012, the parallel Haskell status updates began appearing in the Parallel Haskell Digest. 2011: Parallel and Concurrent Programming in Haskell, a tutorial. version 1.1 released by Simon Marlow Haskell and parallelism, mentioned in an article in the Economist magazine, Jun 2nd 2011. Parallel tree … Read more
Not with array_map, as it doesn’t handle keys. array_walk does: $test_array = array(“first_key” => “first_value”, “second_key” => “second_value”); array_walk($test_array, function(&$a, $b) { $a = “$b loves $a”; }); var_dump($test_array); // array(2) { // [“first_key”]=> // string(27) “first_key loves first_value” // [“second_key”]=> // string(29) “second_key loves second_value” // } It does change the array given as … Read more
Functional languages use a different paradigm than imperative and object-oriented languages. They use side-effect-free functions as a basic building block in the language. This enables lots of things and makes a lot of things more difficult (or in most cases different from what people are used to). One of the biggest advantages with functional programming … Read more