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copied!<p>To expand on the previous answer... for, foreach and map are all higher-order functions - they can all take a function as an argument, so starting here:</p> <pre><code>val list = List(1,2,3) list.foreach(i => println(i * 2)) </code></pre> <p>You have a number of ways that you can make the code more declarative in nature, and cleaner at the same time.</p> <p>First, you don't really need to use the name - <code>i</code> - for each member of the collection, you can use <code>_</code> as a placeholder instead:</p> <pre><code>list.foreach(println(_ * 2)) </code></pre> <p>You can also separate the logic out into a distinct method, and continue to use placeholder syntax:</p> <pre><code>def printTimesTwo(i:Int) = println(i * 2) list.foreach(printTimesTwo(_)) </code></pre> <p>Even cleaner, just pass the raw function without specifying parameters (<em>look ma, no placeholders!</em>)</p> <pre><code>list.foreach(printTimesTwo) </code></pre> <p>And to take it to a logical conclusion, this can be made cleaner still by using <em>infix</em> syntax. Which I show here working with a standard library method. <em>Note: you could even use a method imported from a java library, if you wanted</em>:</p> <pre><code>list foreach println </code></pre> <hr> <p>This thinking extends to anonymous functions and <em>partially-applied functions</em> and also to the map operation:</p> <pre><code>// "2 *" creates an anonymous function that will double its one-and-only argument list map { 2 * } </code></pre> <p>For-comprehensions aren't really very useful when working at this level, they just add boilerplate. But they do come into their own when working with deeper nested structures:</p> <pre><code>//a list of lists, print out all the numbers val grid = List(List(1, 2, 3), List(4, 5, 6), List(7, 8, 9)) grid foreach { _ foreach println } //hmm, could get confusing for(line <- grid; cell <- line) println(cell) //that's clearer </code></pre> <p>I didn't need the <code>yield</code> keyword there, as nothing is being returned. But if I wanted to get back a list of Strings (un-nested):</p> <pre><code>for(line <- grid; cell <- line) yield { cell.toString } </code></pre> <p>With lots of generators, you'll want to split them over multiple lines:</p> <pre><code>for { listOfGrids <- someMasterCollection grid <- listOfGrids line <- grid cell <- line } yield { cell.toString } </code></pre>

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