Re: initializing a static array
On Tuesday, 10 October 2017 at 22:00:27 UTC, kinke wrote: [...] Ah sorry, overlooked that it's the initializer for a struct field.
Re: initializing a static array
On Tuesday, 10 October 2017 at 14:15:07 UTC, Simon Bürger wrote: On Tuesday, 10 October 2017 at 13:48:16 UTC, Andrea Fontana wrote: Maybe: double[n] bar = 0.repeat(n).array; This works fine, thanks a lot. I would have expected `.array` to return a dynamic array. But apparently the compiler is smart enough to know the length. Even the multi-dimensional case works fine: double[n][n] bar = 0.repeat(n).array.repeat(n).array; I hope this is not performance-critical code. The assembly is terrible for such code, at least for LDC, doing a GC allocation, unrolled reset to zero, then memcpying the dynamic array back to the stack: https://godbolt.org/g/uXBN75 `double[n] bar = void; bar[] = 0;` (2 lines, granted) results in a memset.
Re: initializing a static array
On 10/10/2017 03:36 PM, Simon Bürger wrote:
I have a static array inside a struct which I would like to be
initialized to all-zero like so
struct Foo(size_t n)
{
double[n] bar = ... all zeroes ...
}
(note that the default-initializer of double is nan, and not zero)
I tried
double[n] bar = 0; // does not compile
Works for me:
struct Foo(size_t n)
{
double[n] bar = 0;
}
void main()
{
import std.stdio;
Foo!5 foo;
writeln(foo.bar); /* prints "[0, 0, 0, 0, 0]" */
}
Re: initializing a static array
https://run.dlang.io/is/SC3Fks
Re: initializing a static array
Yeah, you are right. My fault. On Tue, Oct 10, 2017 at 4:47 PM, Adam D. Ruppe via Digitalmars-d-learn < digitalmars-d-learn@puremagic.com> wrote: > On Tuesday, 10 October 2017 at 14:42:15 UTC, Daniel Kozak wrote: > >> It will return dynamic array. it is same as: >> >> double[5] = [0,0,0,0,0]; // this is still dynamicaly allocated. >> > > Not true here, the compiler knows it is going into a static array and puts > the result directly in there. It handles literals. > > The range version though will allocate since the function doesn't know > where its result ends up. It will CTFE though if the variable is static. >
Re: initializing a static array
On Tuesday, 10 October 2017 at 14:42:15 UTC, Daniel Kozak wrote: It will return dynamic array. it is same as: double[5] = [0,0,0,0,0]; // this is still dynamicaly allocated. Not true here, the compiler knows it is going into a static array and puts the result directly in there. It handles literals. The range version though will allocate since the function doesn't know where its result ends up. It will CTFE though if the variable is static.
Re: initializing a static array
On Tue, Oct 10, 2017 at 4:15 PM, Simon Bürger via Digitalmars-d-learn < digitalmars-d-learn@puremagic.com> wrote: > On Tuesday, 10 October 2017 at 13:48:16 UTC, Andrea Fontana wrote: > >> On Tuesday, 10 October 2017 at 13:36:56 UTC, Simon Bürger wrote: >> >>> Is there a good way to set them all to zero? The only way I can think of >>> is using string-mixins to generate a string such as "[0,0,0,0]" with >>> exactly n zeroes. But that seems quite an overkill for such a basic task. I >>> suspect I might be missing something obvious here... >>> >> >> Maybe: >> >> double[n] bar = 0.repeat(n).array; >> > > This works fine, thanks a lot. I would have expected `.array` to return a > dynamic array. But apparently the compiler is smart enough to know the > length. Even the multi-dimensional case works fine: > > double[n][n] bar = 0.repeat(n).array.repeat(n).array; > It will return dynamic array. it is same as: double[5] = [0,0,0,0,0]; // this is still dynamicaly allocated.
Re: initializing a static array
On Tuesday, 10 October 2017 at 13:54:16 UTC, Daniel Kozak wrote:
struct Double
{
double v = 0;
alias v this;
}
struct Foo(size_t n)
{
Double[n] bar;
}
Interesting approach. But this might introduce problems later.
For example `Double` is implicitly convertible to `double`, but
`Double[]` is not implicitly convertible to `double[]`. Therefore
I will stick with jmh530's solution for now, but thank you anyway.
Re: initializing a static array
On Tuesday, 10 October 2017 at 13:48:16 UTC, Andrea Fontana wrote: On Tuesday, 10 October 2017 at 13:36:56 UTC, Simon Bürger wrote: Is there a good way to set them all to zero? The only way I can think of is using string-mixins to generate a string such as "[0,0,0,0]" with exactly n zeroes. But that seems quite an overkill for such a basic task. I suspect I might be missing something obvious here... Maybe: double[n] bar = 0.repeat(n).array; This works fine, thanks a lot. I would have expected `.array` to return a dynamic array. But apparently the compiler is smart enough to know the length. Even the multi-dimensional case works fine: double[n][n] bar = 0.repeat(n).array.repeat(n).array;
Re: initializing a static array
On Tuesday, 10 October 2017 at 13:53:37 UTC, jmh530 wrote: double[n] bar; bar[] = 0; This works at runtime only for mutable arrays, anyway.
Re: initializing a static array
On Tuesday, 10 October 2017 at 13:48:16 UTC, Andrea Fontana wrote: Maybe: double[n] bar = 0.repeat(n).array; Alt: double[n] bar; bar[] = 0;
Re: initializing a static array
struct Double
{
double v = 0;
alias v this;
}
struct Foo(size_t n)
{
Double[n] bar;
}
Dne 10. 10. 2017 3:40 odpoledne napsal uživatel "Simon Bürger via
Digitalmars-d-learn" :
I have a static array inside a struct which I would like to be initialized
to all-zero like so
struct Foo(size_t n)
{
double[n] bar = ... all zeroes ...
}
(note that the default-initializer of double is nan, and not zero)
I tried
double[n] bar = 0; // does not compile
double[n] bar = {0}; // neither does this
double[n] bar = [0]; // compiles, but only sets the first element,
ignoring the rest
Is there a good way to set them all to zero? The only way I can think of is
using string-mixins to generate a string such as "[0,0,0,0]" with exactly n
zeroes. But that seems quite an overkill for such a basic task. I suspect I
might be missing something obvious here...
Re: initializing a static array
On Tuesday, 10 October 2017 at 13:36:56 UTC, Simon Bürger wrote: Is there a good way to set them all to zero? The only way I can think of is using string-mixins to generate a string such as "[0,0,0,0]" with exactly n zeroes. But that seems quite an overkill for such a basic task. I suspect I might be missing something obvious here... Maybe: double[n] bar = 0.repeat(n).array;
initializing a static array
I have a static array inside a struct which I would like to be
initialized to all-zero like so
struct Foo(size_t n)
{
double[n] bar = ... all zeroes ...
}
(note that the default-initializer of double is nan, and not zero)
I tried
double[n] bar = 0; // does not compile
double[n] bar = {0}; // neither does this
double[n] bar = [0]; // compiles, but only sets the first
element, ignoring the rest
Is there a good way to set them all to zero? The only way I can
think of is using string-mixins to generate a string such as
"[0,0,0,0]" with exactly n zeroes. But that seems quite an
overkill for such a basic task. I suspect I might be missing
something obvious here...
