ndslice of an array structure member?
Jack Stouffer via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Mon Dec 21 17:13:54 PST 2015
On Monday, 21 December 2015 at 23:59:07 UTC, Jay Norwood wrote:
> I'm trying to learn ndslice. It puzzles me why t3 compiles ok,
> but t4 causes a compiler error in the example below. Should I
> be able to slice a struct member that is an array?
>
> import std.stdio;
> import std.experimental.ndslice;
> import std.experimental.ndslice.iteration: transposed;
> struct sample{
> ulong [10] core_ctr;
> }
>
> struct block{
> ulong[60] samples;
> }
>
> void main() {
> auto a1 = new sample[60];
> auto t3 = a1.sliced!(ReplaceArrayWithPointer.no)(3,4,5);
> auto b1 = new block;
> auto t4 =
> b1.samples.sliced!(ReplaceArrayWithPointer.no)(3,4,5);
> }
The problem is that t3 is slicing a1 which is a dynamic array,
which is a range, while t4 is trying to slice a static array,
which is not a range.
The ranges primitive popFront mutates the length of the range, so
static arrays cannot be used as ranges. But, if you take a slice
of b1.samples, you can use that as a range.
auto t4 = b1.samples[].sliced!(ReplaceArrayWithPointer.no)(3,4,5);
See the section on ranges on this page for more general info on
ranges: http://dlang.org/overview.html
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