ndslice of an array structure member?

[Jay Norwood via Digitalmars-d-learn]

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);
}

== results in error
  Building D project: nd4  

Running: "C:\Program Files\dub\dub.exe" build

Performing "debug" build using dmd for x86.
dip80-ndslice 0.8.4: target for configuration "library" is up to 
date.

nd4 ~master: building configuration "application"...
src\app.d(16,58): Error: template 
std.experimental.ndslice.slice.sliced cannot deduce function from 
argument types !(cast(Flag)false)(ulong[60], int, int, int), 
candidates are:

C:\Users\rlxv10\AppData\Roaming\dub\packages\dip80-ndslice-0.8.4\source\std\experimental\ndslice\slice.d(39,6):
std.experimental.ndslice.slice.sliced(Flag mod = ReplaceArrayWithPointer.yes, Range, 
Lengths...)(Range range, Lengths lengths) if (!isStaticArray!Range && !isNarrowString!Range 
&& allSatisfy!(isIndex, Lengths) && Lengths.length)
C:\Users\rlxv10\AppData\Roaming\dub\packages\dip80-ndslice-0.8.4\source\std\experimental\ndslice\slice.d(47,6):
std.experimental.ndslice.slice.sliced(Flag mod = ReplaceArrayWithPointer.yes, uint N, 
Range)(Range range, auto ref size_t[N] lengths, size_t shift = 0) if (!isStaticArray!Range 
&& !isNarrowString!Range && N)
C:\Users\rlxv10\AppData\Roaming\dub\packages\dip80-ndslice-0.8.4\source\std\experimental\ndslice\slice.d(116,1):
std.experimental.ndslice.slice.sliced(Names...) if (Names.length && 
!anySatisfy!(isType, Names) && allSatisfy!(isStringValue, Names))
dmd failed with exit code 1.
  ^^^ Terminated, exit code: 2 ^^^

Re: ndslice of an array structure member?

[Jack Stouffer via Digitalmars-d-learn]

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

Re: ndslice of an array structure member?

[Jay Norwood via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 01:13:54 UTC, Jack Stouffer wrote:
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.


ok, thanks.  I lost track of the double meaning of static ... I 
normally think of static as variables with static preceding the 
type, allocated at start-up, but in this case it refers to 
structure members that will have a fixed size after the 
allocation.