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    <p>A <code>Range</code> is a special kind of collection that is restricted in what it can represent in order to efficiently perform its operations. It is only able to represent a sequence of numbers with a fixed step in between elements. As such, it only needs to be told about the start, end, and step size in order to be constructed. An <code>Array</code> on the other can hold arbitrary values, so its constructor must be told explicitly what those values are.</p> <p>The definition of <code>Range.apply</code> is that it takes either:</p> <ul> <li>two arguments: a start and end for a range, or </li> <li>three arguments: a start, end, and step size for the range.</li> </ul> <p>Here are the definitions of <code>apply</code> from <code>scala.collection.immutable.Range</code>:</p> <pre><code>/** Make a range from `start` until `end` (exclusive) with given step value. * @note step != 0 */ def apply(start: Int, end: Int, step: Int): Range = new Range(start, end, step) /** Make an range from `start` to `end` inclusive with step value 1. */ def apply(start: Int, end: Int): Range = new Range(start, end, 1) </code></pre> <p>Constrast this with the <code>apply</code> for <code>scala.Array</code>, which accepts a variable-length argument <code>T*</code>:</p> <pre><code>/** Creates an array with given elements. * * @param xs the elements to put in the array * @return an array containing all elements from xs. */ def apply[T: ClassManifest](xs: T*): Array[T] = { val array = new Array[T](xs.length) var i = 0 for (x &lt;- xs.iterator) { array(i) = x; i += 1 } array } </code></pre> <p>If your goal is to have an <code>Array</code> of the numbers 1 to 4, try this:</p> <pre><code>(1 to 4).toArray </code></pre>
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    1. POWhy does val range = Range(1, 2, 3, 4) give error?
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    1. POWhy does val range = Range(1, 2, 3, 4) give error?
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    1. COThere's also the more general `Array.tabulate` where you supply the dimensions and a function describing contents based on its indices, so you don't need a `Range`, e.g. `Array.tabulate(4)(_ + 1)`. But usually you'll just want to use a `Range` directly instead of creating an array, since it's so much cheaper.
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      1. USLuigi Plinge
 

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