Re: Distinguish float and integer types from string
On Saturday, 9 March 2019 at 18:11:09 UTC, Jacob Shtokolov wrote:
I tried to use std.conv.to and std.conv.parse, but found that
they can't really do this. When I call `data.to!int`, the value
of "123.45" will be converted to int!
Are you sure? This here works for me:
import std.stdio;
import std.string;
import std.conv;
void main ()
{
auto s = readln.strip;
try
{
int i = to!int (s);
writefln ("string is an int: %s", i);
}
catch(Exception e)
{
try
{
float f = to!float(s);
writefln ("string is a float: %s", f);
}
catch(Exception e)
{
writefln ("string is an neither an int nor a float:
%s", s);
}
}
}
Re: const pointers C vs. D
On Tuesday, 4 February 2020 at 10:17:39 UTC, Dennis wrote: C++ has a const system that is closer to D's than any other language, but it still has huge differences: Thanks, that clears it up a bit!
const pointers C vs. D
Hi, I'm just wondering about defining const pointers and if there's a difference in C and D. in C, this works: const char* text = "Hello"; text = "world"; but in D it doesn't, because the char* is const. Ff I would like tho have the same behaviour in D as in C, I need to write: const (char)* text = "Hello"; text = "world"; In C, this would not be valid. So the question for me now is: is const char* in D different from C?
Re: sending the address of a struct
On Sunday, 6 September 2020 at 11:10:14 UTC, Simen Kjærås wrote: auto e = receiveOnly!(shared(Env)*); Oh, thanks. Seems, that I just missed that bit with the pranetheses.
sending the address of a struct
Hi,
I have a struct in a separate thread and want to pass it's
address back to the main thread. This is how I think it should
work:
import std.concurrency;
struct Env {}
void run ()
{
shared Env env;
ownerTid.send ();
for (;;) {}
}
void main ()
{
spawn ();
auto e = receiveOnly!(shared Env*);
}
but I'm getting an error when main tries to receive the pointer.
The error message says:
std.concurrency.MessageMismatch@std/concurrency.d(237):
Unexpected message type: expected 'shared(Env*)', got
'shared(test.Env)*'
Now, how can I pass that pointer back to main?
Re: How Stop Worker Thread if Owner Thread is Finished?
You could tell your thread via a shared variable that main has
ended:
import std.stdio;
import std.concurrency;
import core.thread;
shared bool end = false;
void thread ()
{
for (;;)
{
Thread.sleep (500.msecs);
synchronized
{
if (end) break;
}
}
writeln ("thread ends");
}
void main ()
{
spawn ();
Thread.sleep (3.seconds);
writeln ("main ends");
synchronized
{
end = true;
}
}
or you could use the fact, that receiveTimeout throws an
exception, when main ends (although I don't know if this is the
intended behaviour; the manual just says that it throws an
exception when the sending thread was terminated):
import std.stdio;
import std.concurrency;
import core.thread;
void thread ()
{
for (;;)
{
try
{
receiveTimeout (500.msecs);
}
catch (Throwable)
{
break;
}
}
writeln ("thread ends");
}
void main ()
{
auto tid = spawn ();
Thread.sleep (3.seconds);
writeln ("main ends");
}
Re: How to implement Canceleable spawn() from parent
I'm doing this in an X11 application in order to send a timer
event every 100 milliseconds to the main event queue.
class Application
{
shared private bool s_tick;
void clock_task (shared X11.Display* disp, X11.Atom atom,
X11.Window win)
{
for (;;)
{
try
{
receiveTimeout (100.msecs);
if (disp && atomicLoad(s_tick))
{
// disable ticking until it is allowed again at the end
of the event loop
atomicStore(s_tick, false);
X11.XClientMessageEvent event;
event.type = X11.ClientMessage;
event.window = win;
event.message_type = atom;
event.format = 32;
event.data.l = [0, 0, 0, 0, 0];
X11.XSendEvent (cast (X11.Display*) disp, win, 0, 0,
cast(X11.XEvent*));
X11.XFlush (cast (X11.Display*) disp);
}
}
catch (Throwable)
{
return;
}
}
}
this ()
{
...
spawn (_task, cast(shared)x11Display, x11SigClockAtom,
_x11_proxyWindow);
}
run ()
{
while (true)
{
...
// event processing starts here: read in X11 event and
convert it to a wit Event
X11.XEvent x11_event;
X11.XNextEvent (_x11.display, _event);
...
atomicStore(s_tick, true);
}
}
}
Re: Visual D showing weird errors
On Monday, 26 April 2021 at 08:58:25 UTC, Raimondo Mancino wrote: According to -v: DMD64 D Compiler v2.096.0-dirty Well, that says it all, doesn't it? I'm not familiar with the windows versions, but that doesn't seem to be an offical release - at least I never had a dmd2 that claimed to be dirty ;-)
Re: Visual D showing weird errors
On Monday, 26 April 2021 at 10:42:54 UTC, Mike Parker wrote: (According to -v: DMD64 D Compiler v2.096.0-dirty) That's actually normal for the Windows versions. I'm not sure where it comes from, but it's always there. Ouuu, that's bad advertising, isn't it? Who wants to use dirty software, it could infect your computer... :-O
alias this - am I using it wrong?
Hi all,
I have a little problem understanding alias this. I always
thought, that alias this only makes implicit conversions from the
aliased object to this. Then, why do lines 18 and 22 compile in
the code below? And, btw, line 22 crashes with a segmentation
fault.
```d
01 struct Test_Struct {long t;}
02
03 class Alias_Class
04 {
05 Test_Struct ts;
06 alias ts this;
07 }
08
09 class Test_Class
10 {
11 Alias_Class ac;
12 }
13
14 void main ()
15 {
16 auto ac = new Alias_Class;
17 Test_Struct ts = ac; // compiles
18 ac = ts; // compiles as well - why?
19
20 auto tc = new Test_Class;
21 ts = tc.ac; // compiles
22 tc.ac = ts; // again this compiles, but seg
faults
23 }
```
Johann
Re: alias this - am I using it wrong?
On Wednesday, 25 August 2021 at 12:23:06 UTC, Adam D Ruppe wrote:
...
Thanks - that explains in all.
On Wednesday, 25 August 2021 at 12:23:32 UTC, FeepingCreature
wrote:
class Alias_Class
{
Test_Struct ts;
Test_Struct getter() { return ts; }
alias getter this;
}
Good idea, that should solve my current problem. The reason for
having an alias this was that I had a C data type
(cairo_surface_t) that I transferred into a class and I'm using
the alias so that I don't need to rewrite the whole application
at once. Unfortunately I overlooked some code that resulted in a
seg fault - and I was lost at understanding why.
problem with alias this and Tuple
Hi all,
I have a problem with Tuples and struct templates that contain an
alias this:
```d
import std;
struct Element(T)
{
T payload;
alias payload this;
this (T p)
{
payload = p;
}
}
class Item {}
void main ()
{
auto e = Element!Item (new Item());
auto t = tuple(e);
}
```
dmd generates a warning: **Warning: struct Element has method
toHash, however it cannot be called with const(Element!(Item))
this.
Element.toHash defined here:
/usr/local/include/d/druntime/import/object.d(83)**
The culprit seems to be the 'alias payload this'. When I remove
that line, the code works. However, in my code, I need that
alias. Any ideas, what's wrong or what I could do? Thanks.
Re: problem with alias this and Tuple
Thanks, understood. But isn't this a deficiency in the library that should be fixed?
C structs
Hi,
I'm fiddling around with cairo (downloaded
fromhttps://github.com/D-Programming-Deimos/cairo) and I stumbled
over this problem:
(file rectandmatrix.d)
import deimos.cairo.cairo;
void main ()
{
cairo_rectangle_int_t rect;
cairo_matrix_t matrix;
}
Compiling that with 'dmd rectandmatrix' fails with this error:
rectandmatrix.o: In function `_Dmain':
rectandmatrix.d:(.text._Dmain+0x18): undefined reference to
`_D6deimos5cairo5cairo14cairo_matrix_t6__initZ'
collect2: error: ld returned 1 exit status
--- errorlevel 1
The rectangle is OK - no error there. The matrix however,
produces the error. The difference between both is that
cairo_rectangle_int_t is a struct containing integers, and
cairo_matrix_t contains doubles.
I can, however, compile like that:
'dmd rectandmatrix deimos/cairo/cairo.d' (deimos being in a
subdir of the working directory)
then cairo.d is compiled as well and linked to the code.
So, my questions are:
1) Why do I have to compile and link cairo.d - it's only an
definition file for C code and IMHO there shouldn't be any need
to compile cairo.d at all.
2) Why ist a struct containing only integers handled so
differently from a struct holding doubles?
Thanks
Re: C structs
Agreed, but I assumed, that since all definitions in cairo.d are defined as extern (System), (same happens with extern (C), btw.), I would have expected, that D does not implicitly generate initialisation functions. So, why is there no init routine for the rectangle? There's only one for the matrix.
