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POD dynamic array initialization, stride and the index operation
 

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    <p>Sorry, this became a 3-fold question regarding arrays</p> <p>I think (dynamic) arrays are truly powerful in D, but the following has been bothering me for a while:</p> <p>In C++ I could easily allocate an array with designated values, but in D I haven't found a way to do so. Surely the following is no problem:</p> <pre><code>int[] a = new int[N]; a[] = a0; </code></pre> <p>But it looks inefficient, since line one will initialize with <code>0</code>, and like 2 with <code>a0</code>. Could something similar to the following be done in D?</p> <pre><code>int[] a = new int(a0)[N]; // illegal </code></pre> <hr> <p>Another efficiency matter I have when using stride in std.range:</p> <pre><code>import std.stdio; import std.range; struct S { int x; this(this) { writeln("copy ", x); } } void f(S[] s) { } int main() { S[] s = new S[10]; foreach (i, ref v; s) { v.x = i; } f(stride(s, 3)); // error return 0; } </code></pre> <p>Surely I was naive thinking I could simply use stride to create a new array without copying it's elements? There is no way to do so in D, right?</p> <hr> <p>So I went and simulated as if the array was as stride would return, and implemented <code>f</code> as:</p> <pre><code>f(s, 3); void f(S[] s, uint stride) { ref S get(uint i) { assert (i * stride &lt; s.length); return s[i * stride]; } for (uint x ... ) { get(x) = ...; } } </code></pre> <p>Would there be a way to instead write get(x) using the index operator <code>get[x]</code>? This way I could statically mixin / include the striding <code>get</code> function and keep the rest of the function similar. I'd be interested in the approach taken, since a local struct is not allowed to access function scope variables (why not?).</p>
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