Re: question on map
On Wednesday, 12 May 2021 at 09:52:52 UTC, Alain De Vos wrote:
As oppposed to what i expect code below prints nothing nothing
on the screen. What is wrong and how to fix it ?
```
import std.stdio;
import std.range:iota;
import std.algorithm:map;
bool mywriteln(int x){
writeln(x);
return true;
}
void main(){
5.iota.map!mywriteln;
}
```
On Wednesday, 12 May 2021 at 09:52:52 UTC, Alain De Vos wrote:
think lazy :))
5.iota.map!mywriteln.array;
Re: rgba.ptr[0] vs rgba[0]
On Monday, 23 November 2020 at 17:39:09 UTC, Adam D. Ruppe wrote: On Monday, 23 November 2020 at 17:34:27 UTC, visitor wrote: Hi all, I would like to know why in the code below, rgba.ptr[0] is used instead of rgba[0] and allowing the method to be @safe The .ptr[0] skips bounds checking. Since this example is static length with a constant index it shouldn't matter anyway; the compiler can see it is obviously in bounds and skip it too. But if there's any runtime value there's a bounds check with `foo[0]` and that can be surprisingly expensive in certain situations. So `foo.ptr[0]` skipping that can give a nice performance boost. Just without bounds checking the code is obviously trusting the programmer... hence @trusted is required instead of safe. indeed because of the the static length and constant index, it was puzzling me ... Thanks Adam for clarification
rgba.ptr[0] vs rgba[0]
Hi all,
I would like to know why in the code below, rgba.ptr[0] is used
instead of rgba[0] and allowing the method to be @safe
float[4] rgba = 0;
ref inout(float) r() inout pure @trusted { pragma(inline, true);
return rgba.ptr[0]; }
why not :
ref inout(float) r() inout pure @safe { pragma(inline, true);
return rgba[0]; }
avoid an allocation maybe ?
Thanks for your time.
Re: How to use labeled break in static foreach?
https://run.dlang.io/is/xiqi4P not pretty :)) but ...
Re: How to use labeled break in static foreach?
On Wednesday, 9 September 2020 at 17:02:26 UTC, visitor wrote:
On Friday, 14 February 2020 at 06:41:02 UTC, cc wrote:
import std.meta;
enum A = AliasSeq!(1, 2, 3, 4);
static foreach (idx, field; A) {
static if (__traits(compiles, THREELOOP)) {} else {
static if (field == 3) {
pragma(msg, "Got a 3!");
enum THREELOOP = 1; // works with enum, alias etc...
}
static if (idx == A.length - 1) {
static assert(0, "Got no 3...");
}
}
}
https://run.dlang.io/is/BDmIml
oops the online editor saved a mix of an old iteration and a new
one ... (probably my fault)
import std.stdio;
float test(float x)
{
float r = -1;
static foreach(i; 0 .. 100)
{
static if (__traits(compiles, Check)) {} else {
static if (i == 10)
enum Check = 1;
r = i * x;
}
}
return r;
}
void main() {
float ret = test(4.2);
writefln("ret = %s", ret);
}
Re: How to use labeled break in static foreach?
On Friday, 14 February 2020 at 06:41:02 UTC, cc wrote:
import std.meta;
enum A = AliasSeq!(1, 2, 3, 4);
static foreach (idx, field; A) {
static if (__traits(compiles, THREELOOP)) {} else {
static if (field == 3) {
pragma(msg, "Got a 3!");
enum THREELOOP = 1; // works with enum, alias etc...
}
static if (idx == A.length - 1) {
static assert(0, "Got no 3...");
}
}
}
https://run.dlang.io/is/BDmIml
Re: Is there any web browser control in D Lang to display html file ?
On Friday, 16 March 2018 at 20:19:59 UTC, aberba wrote: On Friday, 16 March 2018 at 17:11:17 UTC, visitor wrote: On Friday, 16 March 2018 at 10:31:51 UTC, Jayam wrote: I creating one simple desktop application using dlang. I need to display some html file in my desktop application. How can make it works ? There's also gtkd sourceview : https://github.com/gtkd-developers/GtkD/tree/master/generated/sourceview I think you mean Gtk web view. It comes from WebKit. oh yes, my bad, misreading, i thought OP wanted syntax highlighting and stuff...
Re: Is there any web browser control in D Lang to display html file ?
On Friday, 16 March 2018 at 10:31:51 UTC, Jayam wrote: I creating one simple desktop application using dlang. I need to display some html file in my desktop application. How can make it works ? There's also gtkd sourceview : https://github.com/gtkd-developers/GtkD/tree/master/generated/sourceview
Re: importing std.array: empty in a struct messes things up
On Sunday, 4 March 2018 at 19:53:59 UTC, ag0aep6g wrote:
On 03/04/2018 08:45 PM, ag0aep6g wrote:
I don't know what's going on here. The error message doesn't
make sense to me. Might be a bug in the compiler.
This one works:
struct Stack(T) {
T[] stack;
alias stack this;
bool empty() {return empty(stack);} /* not using UFCS */
import std.array: empty; /* has to come after the method */
}
Looks very much like a compiler bug now. As far as I know, the
order of declarations shouldn't have an effect like that in
structs. And UFCS should also be ok there, as far as I can tell.
?
https://run.dlang.io/is/Ws0qEx
https://run.dlang.io/is/Bancgx
Re: How to concatenate a tuple of strings at compile time?
On Saturday, 6 January 2018 at 19:35:33 UTC, paul wrote:
Hi!
How to concatenate a tuple of strings at compile time?
Something like that maybe ?
import std.stdio;
import std.meta;
enum connected = () {
auto something = AliasSeq!("one", "two", "three");
string res = "";
static foreach(item; something) {{
res ~= item;
}}
return res;
}();
void main()
{
writefln("connected = %s", connected);
}
Re: Putting function pointers / delegates into associative array.
On Thursday, 4 January 2018 at 01:40:21 UTC, Mark wrote:
What I'm trying to do here is to be able to call a function
based off of a key.
class tester {
private void delegate() [char] funcs;
this() {
funcs = ['a': , 'b': ];
}
public void callFuncs(char a) {
funcs[a]();
}
private void A() {
writeln("A");
}
private void B() {
writeln("B");
}
}
Re: Converting array in to aliased tuple type.
On Monday, 25 December 2017 at 21:35:18 UTC, visitor wrote:
On Monday, 25 December 2017 at 21:11:08 UTC, aliak wrote:
On Monday, 25 December 2017 at 17:59:54 UTC, visitor wrote:
On Monday, 25 December 2017 at 15:03:08 UTC, aliak wrote:
On Monday, 25 December 2017 at 14:08:08 UTC, Mengu wrote:
probably better this way
int[2] tmp;
auto points = data.split(':')
.map!( (a) {
a.split(',').map!(to!int).enumerate()
.each!( (i, el) => tmp[i] = el );
return Point(tmp);
} );
Re: Converting array in to aliased tuple type.
On Monday, 25 December 2017 at 21:11:08 UTC, aliak wrote:
On Monday, 25 December 2017 at 17:59:54 UTC, visitor wrote:
On Monday, 25 December 2017 at 15:03:08 UTC, aliak wrote:
On Monday, 25 December 2017 at 14:08:08 UTC, Mengu wrote:
I was kind of hoping for some magical D variadic alias
template on Tuple or something that will just deconstruct the
arguments in to tuple components.
i don't think it's better but :
https://run.dlang.io/is/2rgOzh
Heh, no it's probably not, but interesting! So it does work
with a static array. Is it that .array on a range is not able
to infer a size and hence produce a static array for the given
situation? Is this a D limitation, a logical one or maybe just
not implemented yet?
Cheers!
i don't know the reason, and would be glad to be unlighted :)
There is a Tuple constructor which takes a static array as a
param :
https://dlang.org/phobos/std_typecons.html#.Tuple.this.2
i needed to iterate with an index when building the static array
later, so i transformed the range (a.split(',').map!(to!int))
into a dynamic array, to do so.
one could use std.range enumerate() instead:
auto points = data.split(':')
.map!( a => a.split(',').map!(to!int) )
.map!( (a) {
int[2] staticArray;
foreach (i, el; a.enumerate())
staticArray[i] = el;
return staticArray;
} )
.map!Point;
Cheers
Re: Converting array in to aliased tuple type.
On Monday, 25 December 2017 at 17:59:54 UTC, visitor wrote:
On Monday, 25 December 2017 at 15:03:08 UTC, aliak wrote:
On Monday, 25 December 2017 at 14:08:08 UTC, Mengu wrote:
I was kind of hoping for some magical D variadic alias
template on Tuple or something that will just deconstruct the
arguments in to tuple components.
i don't think it's better but :
https://run.dlang.io/is/2rgOzh
oops sorry, compile time ...
import std.stdio, std.string, std.algorithm, std.conv, std.range;
import std.typecons;
alias Point = Tuple!(int, "x", int, "y");
enum data = "1,2:8,9";
auto points = data.split(':')
.map!( a => a.split(',').map!(to!int).array )
.map!( (da) {
int[2] staticArray;
foreach (i, el; da)
staticArray[i] = el;
return staticArray;
} )
.map!Point ;
void main()
{
writefln("points : %s", points);
}
Re: Converting array in to aliased tuple type.
On Monday, 25 December 2017 at 15:03:08 UTC, aliak wrote: On Monday, 25 December 2017 at 14:08:08 UTC, Mengu wrote: I was kind of hoping for some magical D variadic alias template on Tuple or something that will just deconstruct the arguments in to tuple components. i don't think it's better but : https://run.dlang.io/is/2rgOzh
Re: Allocating a class within another class during object init w/o passing in an allocator
On Thursday, 15 December 2016 at 17:44:23 UTC, David Zhang wrote:
would something like this be a solution ?
import std.stdio;
import std.experimental.allocator;
class SomeClass {
int someint = 42;
static SomeClass opCall(int a) {
auto inst = theAllocator.make!SomeClass;
inst.someint += a;
return inst;
}
void destruct() {
theAllocator.dispose(this);
}
}
class Foo {
this() {
sc = SomeClass(7);
sc.someint -= 42;
}
~this() {
sc.destruct();
}
size_t something;
SomeClass sc;
}
void main(string[] args) {
auto foo = theAllocator.make!Foo;
assert(foo.sc.someint == 7);
theAllocator.dispose(foo);
}
Re: functional way doing array stuff/ lambda functions
On Monday, 14 December 2015 at 11:45:50 UTC, Namal wrote:
foreach(k;1..11){
auto t = prim_factors(k,P);
v~= [k,product(t)];
}
it crashes because your first t in the loop is an empty array
because 1 is not a prime ( in "prim_sieve" : T[1] = true)
later when you loop starting with k = 1, prim_factors(1,P) gives
you back an empty array.
so either loop through 2..11 or guard against the empty array
if (!t.empty) v~= [k, product(t)];
i don't think you need any ref in your functions parameters, as a
slice is already a reference
http://dlang.org/spec/arrays.html#slicing
Re: functional way doing array stuff/ lambda functions
On Sunday, 13 December 2015 at 03:08:33 UTC, Namal wrote:
This works for me :
import std.stdio, std.algorithm, std.range;
int[] prim_factors(int n, const int[] P) {
int[] v;
P.filter!( x => x*x <= n).each!( (i) {
while (n % i == 0) {
v ~= i;
n /= i;
if (i == 1) break; // infinite loop otherwise !
}
} );
if (n > 1) v ~= n;
return v.sort.uniq.array;
}
void main(string[] args) {
int[] P = [1,2,3,4,5];
writeln( prim_factors(10, P).reduce!((r, i) => r*i)() );
}
Re: benchmark on binary trees
ok, i have a working version (memory is nice, twice the speed as non parallel) ; http://dpaste.dzfl.pl/504a652c6c47 real0m14.427s user1m19.347s sys 0m0.124s i've got similar performances, without Allocators, using directly malloc and free i had to recursively deallocate ... though, still far from competing with the fastest, any advice ? i guess FreeList allocator is not the better tool here ?
Re: benchmark on binary trees
version with apr (like in c version) http://dpaste.dzfl.pl/68c0157225e7 compiled with ldc it's indeed a bit faster on average : real0m1.999s user0m9.810s sys 0m0.148 btw Rust version is even faster than my little bit outdated gcc (4.9) latest try with allocators : http://dpaste.dzfl.pl/86b9b3c4ad71 swallows huge memory, slow ! what am i doing wrong ? (concurrency problem ?)
Re: benchmark on binary trees
using Apache Portable Runtime(APR) like in the C version : http://dpaste.dzfl.pl/6ca8b5ffd6dc works like a charm, 2.061s on my machine ! if file name is binarytrees.d dmd -w -inline -O -release -I/usr/include/apr-1.0 -L/usr/lib/x86_64-linux-gnu/libapr-1.so -of"binarytrees" "binarytrees.d" measured with "time ./binarytrees 20" on command line: real0m2.061s user0m8.156s sys 0m0.181s C version gives : real0m1.892s user0m9.087s sys 0m0.188s Not bad !!! :-D Still i would like to know what i'm doing wrong with the allocator's version, besides the fact that apr tools are doing more sophisticated work than my naive approach :-D ?
Re: benchmark on binary trees
C++ version : real0m3.587s user0m9.211s sys 0m7.341s
Re: benchmark on binary trees
On Monday, 7 December 2015 at 10:55:25 UTC, Alex wrote: On Sunday, 6 December 2015 at 12:23:52 UTC, visitor wrote: Hello, interesting exercise for me to learn about allocators :-) Nice to know, a novice can inspire someone :) i managed to parallelize the code reaching similar performance, in terms of speed, as the non parallel version : http://dpaste.dzfl.pl/6c3e6edcff59 Cool! This is what I looked for! BUT it consumes insane memory, don't try with argument more than 17 !!! I assume, the allocator itself is something, that is not really needed in this case. Maybe, there is a more straight forward access to the problem. Even a simpler then in all the versions on the benchgame site, but I don't see it right now. And with the allocator attempt I had a chance to experiment with the experimental module and to write a very quick copy of a program, which I want to have... i've got more speed improvement with "taskPool.parallel(depthind, 2)" in the foreach parallel loop : second argument are workUnits (2 for me, on a quad core gave best results) Also using directly "FreeList!(Mallocator, Tree_node.sizeof)" without wrapping it in an allocatorObject gives speed improvement (with changes to makeTree method) i took inspiration from the C code, they use a memory pool management, like anonymous already pointed in c++ version, which i think could (must?) be achieved with allocators, to gain speed i think it's a key point, no GC !! FreeList allocator appears (to me) as a good candidate for this. but as i'm new to this, i'm sure to not doing it the right way ! i tried the exact same FreeList allocator but backed with the GCAllocator (not the Mallocator used in my code), then memory consumption is very good but of course it"s slow ! i tried a lot of other allocators, variations on the presented code, but memory management is awful :(
Re: benchmark on binary trees
On Sunday, 6 December 2015 at 08:35:33 UTC, Alex wrote: Thanks for commenting to everyone! If anybody has further ideas - all of them would be appreciated :) The original site is not interested in any further languages to be tested, so my experiment ends here for now... Hello, interesting exercise for me to learn about allocators :-) i managed to parallelize the code reaching similar performance, in terms of speed, as the non parallel version : http://dpaste.dzfl.pl/6c3e6edcff59 BUT it consumes insane memory, don't try with argument more than 17 !!! so either i'm doing something stupid (in parallel code, i guess) or the FreeList allocator is totally not the right tool ... (both ?) some light-shedding would be really appreciated, Thanks
Re: Pixelbuffer to draw on a surface
gtkd demos for examples, might be of interest, like clock : https://github.com/gtkd-developers/GtkD/blob/master/demos/cairo/cairo_clock/clock.d
Re: having problem with `std.algorithm.each`
On Monday, 30 November 2015 at 09:56:08 UTC, ref2401 wrote:
DMD 2.069.1
OS Win8.1 Enterprise
in a multiline statement, i believe you must use :
arr.each!((ref e) {
writeln(e);
++e;
})
"=>" is for oneliner
though i don"t understand why it fails silently ??
Re: Pixelbuffer to draw on a surface
but there is no specific solution inside GTKD? for example, in pseudo code auto surf = new Surface(...); // look for cairo.Surface doc auto cr = cairo.Context.Context.create(surf); // pb is an existing gdkpixbuf.Pixbuf gdk.Cairo.setSourcePixbuf(cr, pb, width, height); cr.paint(); adding onDraw event listener on the widget owner of the Pixbuf (gtk.Image for example)
Re: having problem with `std.algorithm.each`
On Monday, 30 November 2015 at 12:03:08 UTC, anonymous wrote:
On 30.11.2015 11:50, visitor wrote:
though i don"t understand why it fails silently ??
ref2491's original code is valid, but doesn't have the intended
meaning. `e => {foo(e);}` is the same as `(e) {return ()
{foo(e);};}`, i.e. a (unary) function that returns a (nullary)
delegate. Calling it does not run foo. In contrast, calling
this runs foo: `e => foo(e)`.
`e => {foo(e);}` is the same as `(e) {return () {foo(e);};}`
Ok, Thanks ! :-)
