Re: Unexpected behavior when casting away immutable
On Wednesday, 23 September 2015 at 11:38:38 UTC, Mafi wrote: On Wednesday, 23 September 2015 at 05:24:05 UTC, John Colvin wrote: On Wednesday, 23 September 2015 at 03:39:02 UTC, Mike Parker wrote: ... ``` immutable int x = 10; int* px = cast(int*) *px = 9; writeln(x); ``` It prints 10, where I expected 9. This is on Windows. I'm curious if anyone knows why it happens. violating immutable is undefined behaviour, so the compiler is technically speaking free to assume it never happens. At the very least, neither snippet's result is guaranteed to show a change or not. At the most, literally anything can happen. In essence, this code snippet is even better than the OP expected in showing why you shouldn't cast away immutable. Yes, that's true. I think using both snippets drives the point home pretty well.
dis...@dlang.org
I am just starting to look into D and i have to say I am loving it at the moment. But I have ran into an issue that i can't seem to find any libraries for Api hooking. If anyone knows of a well documented source for this it would be much appreciated.
Re: Unexpected behavior when casting away immutable
On Wednesday, 23 September 2015 at 05:24:05 UTC, John Colvin wrote: On Wednesday, 23 September 2015 at 03:39:02 UTC, Mike Parker wrote: ... ``` immutable int x = 10; int* px = cast(int*) *px = 9; writeln(x); ``` It prints 10, where I expected 9. This is on Windows. I'm curious if anyone knows why it happens. violating immutable is undefined behaviour, so the compiler is technically speaking free to assume it never happens. At the very least, neither snippet's result is guaranteed to show a change or not. At the most, literally anything can happen. In essence, this code snippet is even better than the OP expected in showing why you shouldn't cast away immutable.
Re: Unexpected behavior when casting away immutable
On Wednesday, 23 September 2015 at 14:34:07 UTC, bachmeier wrote: I was not aware that you could "violate" immutable. In that case, it's not immutable. You can violate absolutely everything in a system language with casts and pointers. That is exactly what makes it system language. But you do so only by intentionally and explicitly abandoning type system and domain of well-defined behaviour. Compiler could as well decide to put it in RO section of executable resulting in app crash at runtime (that happens with string literals on Linux). Any cast means "I know what I am doing and I am fully prepared to get burned".
Re: Unexpected behavior when casting away immutable
On Wednesday, 23 September 2015 at 14:34:07 UTC, bachmeier wrote: On Wednesday, 23 September 2015 at 05:24:05 UTC, John Colvin wrote: violating immutable is undefined behaviour, so the compiler is technically speaking free to assume it never happens. At the very least, neither snippet's result is guaranteed to show a change or not. At the most, literally anything can happen. I was not aware that you could "violate" immutable. In that case, it's not immutable. immutable is guaranteed to be enforced at the type-system level. If you deliberately break the type system and tell the compiler to modify data that in actual fact is immutable, then that is undefined behaviour. If you're lucky, the data could have some protection such that writing to it will trigger a fault at the hardware level, but that's definitely *not* guaranteed.
Re: scope in function argument
On Wednesday, 23 September 2015 at 17:09:40 UTC, Freddy wrote:
What does it mean when there is a scope in a function argument.
That you are not supposed to let that reference escape the
function scope. The compiler does little verification of this
right now, but may optimize on that assumption (notably, scope
delegates will not be copied to the heap right now).
In the future, it may become an error to allow them to escape.
int* b;
void func(scope int* a) {
b = a; // you made a escape the function scope, undefined
behavior results
}
scope in function argument
What does it mean when there is a scope in a function argument.
---
void func(scope int* a){}
---
Re: scope in function argument
On 09/23/2015 10:11 AM, Adam D. Ruppe wrote: > On Wednesday, 23 September 2015 at 17:09:40 UTC, Freddy wrote: >> What does it mean when there is a scope in a function argument. > > That you are not supposed to let that reference escape the function > scope. Just to complete with a related feature, here are also 'return' parameters, which make the compiler ensure that the returned reference lives longer than the 'ref' argument. Unfortunately, I can't see that feature here anymore: http://dlang.org/function.html#parameters Has it been pulled back? It still works in 2.068. I had written about it: http://ddili.org/ders/d.en/function_parameters.html#ix_function_parameters.return,%20parameter Then there is the -dip25 compiler switch that forces the programmer to put 'return' on every returned 'ref' parameter, effectively enforcing that check: http://wiki.dlang.org/DIP25 Ali
Re: Dub package with C code
On Thursday, 24 September 2015 at 04:17:14 UTC, Rikki Cattermole wrote: Is libxlsxwriter available in the systems package manager? Pacman says no. Let e.g. Windows users figure theirs out. libxlsxwriter is not supported on windows. Which is kind-of funny.
Re: dis...@dlang.org
On 09/23/2015 06:01 AM, Aidan wrote: I am just starting to look into D and i have to say I am loving it at the moment. But I have ran into an issue that i can't seem to find any libraries for Api hooking. If anyone knows of a well documented source for this it would be much appreciated. I don't understand the question but it may be related to lack of fiber in one's diet: :) http://vibed.org/features#fibers http://ddili.org/ders/d.en/fibers.html Ali
Re: dis...@dlang.org
http://forum.dlang.org/thread/hrzfcjrltftgzansd...@forum.dlang.org https://github.com/Trass3r/hooksample
What's wrong with this BinaryHeap declaration line? Assertion failure in std.container.array.d
What I HAD TO do to get it to compile:
programResultsQ = heapify!(compareResults,
Array!(Results!(O,I)))(Array!(Results!(O,I))([Results!(O,I)()]),
1);
programResultsQ.popFront();
What running it says:
AssertionFailure at line 381 of std.container.array.d, which
looks like:
/**
Constructor taking a number of items
*/
this(U)(U[] values...) if (isImplicitlyConvertible!(U, T))
{
import std.conv : emplace;
auto p = cast(T*) malloc(T.sizeof * values.length);
static if (hasIndirections!T)
{
if (p)
GC.addRange(p, T.sizeof * values.length);
}
foreach (i, e; values)
{
emplace(p + i, e);
assert(p[i] == e); /* THIS IS LINE 381 */
}
_data = Data(p[0 .. values.length]);
}
Any ideas. How can I improve this declaration? Using Phobos
sometimes is such a mystery.
Re: What's wrong with this BinaryHeap declaration line? Assertion failure in std.container.array.d
On Wednesday, 23 September 2015 at 05:56:08 UTC, Enjoys Math
wrote:
What I HAD TO do to get it to compile:
programResultsQ = heapify!(compareResults,
Array!(Results!(O,I)))(Array!(Results!(O,I))([Results!(O,I)()]), 1);
programResultsQ.popFront();
What running it says:
AssertionFailure at line 381 of std.container.array.d, which
looks like:
/**
Constructor taking a number of items
*/
this(U)(U[] values...) if (isImplicitlyConvertible!(U, T))
{
import std.conv : emplace;
auto p = cast(T*) malloc(T.sizeof * values.length);
static if (hasIndirections!T)
{
if (p)
GC.addRange(p, T.sizeof * values.length);
}
foreach (i, e; values)
{
emplace(p + i, e);
assert(p[i] == e); /* THIS IS LINE 381 */
}
_data = Data(p[0 .. values.length]);
}
Any ideas. How can I improve this declaration? Using Phobos
sometimes is such a mystery.
I mean initialization...
Here's the corresponding declaration:
alias ProgramResultsQueue(O,I) =
BinaryHeap!(Array!(Results!(O,I)), compareResults); /* module
scope */
ProgramResultsQueue!(O,I) programResultsQ; /* class member */
The intialization line occurs in the class's ctor.
Re: Why is the constructor of B called?
On Wednesday, 23 September 2015 at 21:14:17 UTC, Adam D. Ruppe wrote: On Wednesday, 23 September 2015 at 21:08:37 UTC, tcak wrote: I wouldn't expect B's constructor to be called at all unless "super" is used there. "If no call to constructors via this or super appear in a constructor, and the base class has a constructor, a call to super() is inserted at the beginning of the constructor. " from http://dlang.org/class.html#constructors the idea is to make sure the base class construction work is done too. Is there any way to prevent this behaviour? Quickly checked whether Java acts in the same way. Answer is yes.
Re: Why is the constructor of B called?
On Wednesday, 23 September 2015 at 21:08:37 UTC, tcak wrote: I wouldn't expect B's constructor to be called at all unless "super" is used there. "If no call to constructors via this or super appear in a constructor, and the base class has a constructor, a call to super() is inserted at the beginning of the constructor. " from http://dlang.org/class.html#constructors the idea is to make sure the base class construction work is done too.
Re: Is there a smart way to process a range of range by front ?
On Wednesday, 23 September 2015 at 21:04:44 UTC, Justin Whear wrote: On Wed, 23 Sep 2015 20:48:03 +, BBasile wrote: I was thinking to a general *interleave()* algorithm for any compatible Range of Range but I can't find any smart way to process each sub range by front Can you show a sample input and output to clarify what you mean by interleave? It's possible that what you want is std.range.frontTransversal, std.range.transversal, or std.range.transposed. --- auto r0 = [[0,2],[1,3]]; auto r1 = interleave(r0); assert(r1 = [0,1,2,3]); auto r2 = [[0,3],[1,4],[2,5]]; auto r3 = interleave(r2); assert(r3 = [0,1,2,3,4,5]); --- the fact that the numbers are ordered is just an helper.
Re: Is there a smart way to process a range of range by front ?
On Wed, 23 Sep 2015 21:17:27 +, BBasile wrote: > On Wednesday, 23 September 2015 at 21:04:44 UTC, Justin Whear wrote: >> On Wed, 23 Sep 2015 20:48:03 +, BBasile wrote: >> >>> I was thinking to a general *interleave()* algorithm for any >>> compatible Range of Range but I can't find any smart way to process >>> each sub range by front >> >> Can you show a sample input and output to clarify what you mean by >> interleave? It's possible that what you want is >> std.range.frontTransversal, std.range.transversal, or >> std.range.transposed. > > --- > auto r0 = [[0,2],[1,3]]; > auto r1 = interleave(r0); > assert(r1 = [0,1,2,3]); > auto r2 = [[0,3],[1,4],[2,5]]; > auto r3 = interleave(r2); > assert(r3 = [0,1,2,3,4,5]); > --- > > the fact that the numbers are ordered is just an helper. OK, I think what you're after is std.range.roundRobin.
Re: Is there a smart way to process a range of range by front ?
On Wednesday, 23 September 2015 at 21:17:29 UTC, BBasile wrote: On Wednesday, 23 September 2015 at 21:04:44 UTC, Justin Whear wrote: On Wed, 23 Sep 2015 20:48:03 +, BBasile wrote: I was thinking to a general *interleave()* algorithm for any compatible Range of Range but I can't find any smart way to process each sub range by front Can you show a sample input and output to clarify what you mean by interleave? It's possible that what you want is std.range.frontTransversal, std.range.transversal, or std.range.transposed. --- auto r0 = [[0,2],[1,3]]; auto r1 = interleave(r0); assert(r1 = [0,1,2,3]); auto r2 = [[0,3],[1,4],[2,5]]; auto r3 = interleave(r2); assert(r3 = [0,1,2,3,4,5]); --- the fact that the numbers are ordered is just an helper. just imagine that there are double equal symbols in the assertions...
Re: Is there a smart way to process a range of range by front ?
On Wednesday, 23 September 2015 at 21:24:22 UTC, Justin Whear
wrote:
On Wed, 23 Sep 2015 21:17:27 +, BBasile wrote:
On Wednesday, 23 September 2015 at 21:04:44 UTC, Justin Whear
wrote:
On Wed, 23 Sep 2015 20:48:03 +, BBasile wrote:
I was thinking to a general *interleave()* algorithm for any
compatible Range of Range but I can't find any smart way to
process each sub range by front
Can you show a sample input and output to clarify what you
mean by interleave? It's possible that what you want is
std.range.frontTransversal, std.range.transversal, or
std.range.transposed.
---
auto r0 = [[0,2],[1,3]];
auto r1 = interleave(r0);
assert(r1 = [0,1,2,3]);
auto r2 = [[0,3],[1,4],[2,5]];
auto r3 = interleave(r2);
assert(r3 = [0,1,2,3,4,5]);
---
the fact that the numbers are ordered is just an helper.
OK, I think what you're after is std.range.roundRobin.
---
import std.range;
auto interleave(RoR)(RoR r)
{
return r.transposed.join;
}
void main()
{
auto r0 = [[0,2],[1,3]];
auto r1 = interleave(r0);
assert(r1 == [0,1,2,3]);
auto r2 = [[0,3],[1,4],[2,5]];
auto r3 = interleave(r2);
assert(r3 == [0,1,2,3,4,5]);
}
--
thx, but as you was suposing initially 'transposed' works.
didn't know this function before. works fine.
Re: Why is the constructor of B called?
On 09/23/2015 02:25 PM, tcak wrote: On Wednesday, 23 September 2015 at 21:14:17 UTC, Adam D. Ruppe wrote: On Wednesday, 23 September 2015 at 21:08:37 UTC, tcak wrote: I wouldn't expect B's constructor to be called at all unless "super" is used there. "If no call to constructors via this or super appear in a constructor, and the base class has a constructor, a call to super() is inserted at the beginning of the constructor. " from http://dlang.org/class.html#constructors the idea is to make sure the base class construction work is done too. Is there any way to prevent this behaviour? No and I don't think it will ever be implemented. The derived class is supposed to be used as the super class, which involves proper construction of the super parts. Quickly checked whether Java acts in the same way. Answer is yes. Same with C++. As discussed in the other thread, at least D allows changing the order in which the super constructor is executed. Ali
Is there a smart way to process a range of range by front ?
I was thinking to a general *interleave()* algorithm for any
compatible Range of Range but I can't find any smart way to
process each sub range by front, eg:
---
void interleave(RoR)(RoR r)
{
r.each!(a => a.writeln);
}
void main()
{
auto r = [[0,2],[1,3]];
interleave(r);
}
---
will print:
[0,2]
[1,3]
while to interleave i need to take the front of each sub range
before poping each ror element.
Currently I'm here (don't run this ;)) :
---
auto interleave(RoR)(RoR r)
{
alias T = ElementType!r[0];
T[] result;
while (!empty(r[0]))
r.each!(a => (result ~= a.front, a.popFront));
return result;
}
void main()
{
auto r = [[0,2],[1,3]];
interleave(r);
}
---
but it doesn't work because 'a' is not consumed. It looks like
it's saved from the input parameter at each iteration of the
while loop hence it never returns.
Is it possible ?
Why is the constructor of B called?
[code]
import std.stdio;
class B {
this() {
writeln("B.constructor");
foo();
}
void foo() {
writeln("B.foo");
}
}
class D : B {
this() {
writeln("D.constructor");
}
override void foo() {
writeln("D.foo overrides B.foo");
}
}
void main() {
auto b = new D();
}
[/code]
Result:
B.constructor
D.foo overrides B.foo
D.constructor
There is no use of "super()" in the constructor of D, yet B's
constructor is called when D is created. Why is that so?
I changed the constructor of D as follows:
[code]
this() {
super();
writeln("D.constructor");
}
[/code]
Results haven't changed at all. "super()" doesn't make any
difference. What's going on?
I wouldn't expect B's constructor to be called at all unless
"super" is used there.
Re: Is there a smart way to process a range of range by front ?
On Wed, 23 Sep 2015 20:48:03 +, BBasile wrote: > I was thinking to a general *interleave()* algorithm for any compatible > Range of Range but I can't find any smart way to process each sub range > by front Can you show a sample input and output to clarify what you mean by interleave? It's possible that what you want is std.range.frontTransversal, std.range.transversal, or std.range.transposed.
Re: Dub package with C code
On 24/09/15 2:43 PM, Sebastiaan Koppe wrote: I have just created bindings for libxlsxwriter, an c library for creating excel files. Used the htod tool to do most of the work, and only had to adjust some things - mainly because libxlsxwriter uses data structures written in macro's. Right now I am making a dub package and I would like to aim for convenience for end-users (read: me). Therefor I decided to include the compiled static library inside the package. I only use Linux 64-bit myself, but this is obviously limiting for other people. The other option I had was to include the whole c code, depend on gcc or clang, and have dub (somehow) first build libxlsxwriter. But that seemed a bit too much... Another option would be to require end-users to build libxlsxwriter themselves. What do you guys recommend? Is libxlsxwriter available in the systems package manager? If so, I would just link against that. Preferably the shared library. Let e.g. Windows users figure theirs out.
Dub package with C code
I have just created bindings for libxlsxwriter, an c library for creating excel files. Used the htod tool to do most of the work, and only had to adjust some things - mainly because libxlsxwriter uses data structures written in macro's. Right now I am making a dub package and I would like to aim for convenience for end-users (read: me). Therefor I decided to include the compiled static library inside the package. I only use Linux 64-bit myself, but this is obviously limiting for other people. The other option I had was to include the whole c code, depend on gcc or clang, and have dub (somehow) first build libxlsxwriter. But that seemed a bit too much... Another option would be to require end-users to build libxlsxwriter themselves. What do you guys recommend?
Re: Is there a smart way to process a range of range by front ?
On Wednesday, 23 September 2015 at 21:30:37 UTC, BBasile wrote:
auto interleave(RoR)(RoR r)
{
return r.transposed.join;
If you use joiner it will even be lazy and avoid the allocation.
Re: Why is the constructor of B called?
On Wed, Sep 23, 2015 at 03:25:04PM -0700, Ali Çehreli via Digitalmars-d-learn wrote: > On 09/23/2015 02:25 PM, tcak wrote: > >On Wednesday, 23 September 2015 at 21:14:17 UTC, Adam D. Ruppe wrote: > >>On Wednesday, 23 September 2015 at 21:08:37 UTC, tcak wrote: > >>>I wouldn't expect B's constructor to be called at all unless > >>>"super" is used there. > >> > >>"If no call to constructors via this or super appear in a > >>constructor, and the base class has a constructor, a call to super() > >>is inserted at the beginning of the constructor. " > >> > >> > >>from http://dlang.org/class.html#constructors > >> > >>the idea is to make sure the base class construction work is done > >>too. > > > >Is there any way to prevent this behaviour? > > No and I don't think it will ever be implemented. The derived class is > supposed to be used as the super class, which involves proper > construction of the super parts. [...] I can't think of any valid use case for not running the base class ctor. Are you sure you aren't violating the Liskov Substitution Principle in some way? It may be that what you need is a has-a relationship rather than an is-a relationship in your class. T -- Once the bikeshed is up for painting, the rainbow won't suffice. -- Andrei Alexandrescu
Re: Why is the constructor of B called?
On Wednesday, 23 September 2015 at 21:25:15 UTC, tcak wrote: On Wednesday, 23 September 2015 at 21:14:17 UTC, Adam D. Ruppe wrote: On Wednesday, 23 September 2015 at 21:08:37 UTC, tcak wrote: I wouldn't expect B's constructor to be called at all unless "super" is used there. "If no call to constructors via this or super appear in a constructor, and the base class has a constructor, a call to super() is inserted at the beginning of the constructor. " from http://dlang.org/class.html#constructors the idea is to make sure the base class construction work is done too. Is there any way to prevent this behaviour? Quickly checked whether Java acts in the same way. Answer is yes. You might be able to swap out the vtbl entry for a stub call it and trick the compiler and swap it back, but...
