<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>My favorite proposal so far is one that was posted a while ago, [Int * 4]. <span style="background-color: rgba(255, 255, 255, 0);">I think that this syntax looks pretty Swifty. There isn't an oddball subscript operator like with Int[4], and there isn't a need to allow generics to support values as parameters. </span>It's clear that [Int * 4] will be array-like and contain four Ints. For multidimensional arrays we could use [Int * (2,3)]. For an array of tuples, [(x: Int, y: Int) * 4]. I'm not sure why nested static arrays would be needed when multidimentionality is provided out of the box, but presumably the syntax would support them; you would just need to subscript the arrays one at a time instead of with a single subscript operator, e.g., a[i][j] instead of a[i, j].</div><div><br></div><div>I'm imagining this syntax working like [T] does now as a shorthand for Array<T>, although I'm not sure what [Int * 4] should be short for (StaticArray<Int, 4>? Vector4<Int>? ...). Constructors for static arrays would be called using [Int * 4](args). I'm thinking the constructors would be [T * 4](filledWith: T), [T * 4](filledBy: (Int)->T), and an initializer taking a Sequence that fails in some manner on a dimension mismatch.</div><div><br></div><div><br>On Jun 1, 2017, at 7:36 AM, Haravikk via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br><br></div><blockquote type="cite"><div>Just wanted to add my two-cents to this discussion, but in terms of syntax I think that the basic method for specifying size should be with some kind of type variables, like so:<br class=""><div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>struct MyFixedArray<T, size:Int> { … }</font></div><div class=""><br class=""></div><div class="">The idea being that we can then use size as a variable anywhere within the code for MyFixedArray, but unlike other variables it is determined at compile time, so should be optimised accordingly. As with generics, setting a type variable effectively creates a variant type so for example, a MyFixedArray<Int, size:3> and a MyFixedArray<Int, size:4> would no longer be directly compatible as they may differ internally.</div><div class=""><br class=""></div><div class="">This would be useful not just for fixed arrays, but other possibly type variations as well. Ideally it should be possible to specify a default value for type variables; while this wouldn't be useful for fixed arrays, it may be useful for other type variants.</div><div class=""><br class=""></div><div class="">To better suit the specific use-case of arrays, we could also add some useful attributes or keywords, for example, reusing subscript could give us:</div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><font face="Monaco" class="">struct MyFixedArray<T, subscript size:Int> { … }</font></div><div class=""><font face="Monaco" class="">let foo:MyFixedArray[4] = [1, 2, 3, 4] // with T being inferred, this is a shorthand for specifying a size of 4</font></div></blockquote><font face="Monaco" class=""><br class=""></font>Type variables could also be usable with generics, like-so:<div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><span style="font-family: Monaco;" class="">// only accept fixed arrays of same or smaller size:</span></div></blockquote><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><font face="Monaco" class="">func myMethod<FA>(values:FA) where FA:FixedArray, FA.size <= Self.size { … } </font></div></blockquote><div class=""></div><div class=""><div class=""><br class=""></div><div class="">These are the kind of general purpose capabilities I'd like to see at some point, as the usefulness extends beyond just fixed-size arrays.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">However, on the subject of fixed-size arrays specifically, one other possibility to explore is the concept of Tuple repetition and subscripting. For example, it would be interesting if we could do things like:</div><div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>var foo:(Int)[4] = 0 // Initialises four Ints, all set initially to zero</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>for i in 0 ..< 4 { foo[i] = i } // values are no 0, 1, 2, 3</font></div><div class=""><br class=""></div><div class="">This can be especially interesting when you get into more complex tuples like so:</div><div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>var bar:(x:Int, y:Int)[10] = (x: 0, y: 0) // Initialises 10 pairs of Ints, all initially set to zero</font></div></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>for i in 0 ..< 10 { bar[i].x = i; bar[i].y = i } // here we need to use .x and .y to access the values of each pair</font></div><div class=""><br class=""></div><div class="">Of course this would have the same performance characteristics as standard tuples, but it's an interesting means for creating quick, fixed-size arrays in a flexible way. Part of the idea here is that by subscripting tuples, we avoid the need for a general subscript on all types, keeping that available for use-cases like the above.</div></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>swift-evolution mailing list</span><br><span><a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a></span><br><span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution">https://lists.swift.org/mailman/listinfo/swift-evolution</a></span><br></div></blockquote></body></html>