Re: is this a poly Polymorphism?
On 2011-08-29 01:58:30 +, Jonathan M Davis jmdavisp...@gmx.com said:
On Monday, August 29, 2011 04:50:09 hhaammaadd wrote:
import std.stdio;
class employee {
void work() {
writeln(I am employee);
}
}
class manager: employee {
void work() {
writeln(I am manager);
}
}
void main() {
employee e1 = new manager;//here
e1.work();
manager m3 = new manager;//--|here
employee *e2 = m3;//|
e2.work();
}
Pointers are not polymorphic in D. Class references are, but if you have a
pointer to a class, it assumes that the type is exactly that type and
determines its function calls at compile time rather than at runtime.
Actually, a pointer to a class is really a pointer to a reference to an
object, since the reference is always with a class type. So employee
* is in reality a pointer to a reference to an employee object.
--
Michel Fortin
michel.for...@michelf.com
http://michelf.com/
Re: d2 file input performance
On 8/26/11 23:56 , bearophile wrote: Steven Schveighoffer: In fact, it would probably be faster. I suggest the OP to keep us updated on this matter. And later after some time, if no solutions are found, to bring the issue to the main D newsgroup and to Bugzilla too. This is a significant issue. Bye, bearophile Small update: I added some more example implementations as a reaction to Mehrdad's suggestion to make sure to use the same file-read api. So the c++ and the d version both load libc dynamically and from that the symbol fread. respective times from c++ and d: 115ms vs. 504ms. the only thing i could also try is to use ldc or gdc (but i first have to install those). regards christian
Re: Memory leak with BufferedFile?
On 8/28/11 1:00 , Leon wrote: I'm writing a simple program which uses merge sort to sort very large text files. I split the text file into several temporary files which are sorted and merged together. The trouble I'm having is that the BufferedFile class seems to have a memory leak. The memory usage of the process slowly goes up until it throws an out of memory exception. I can fix the memory leak by switching to the File class, but that makes the program much slower. Calling GC.collect() didn't help, and neither did explicitly deleting the BufferedFile object. Thats very interesting! Perhaps you can have a look at: https://github.com/gizmomogwai/performance There I ran into performanceproblems using BufferedFile. One of the best solutions I found till now is using mmfile as in https://github.com/gizmomogwai/performance/blob/master/src/d/readbytes5.d. Perhaps this could be of help for you. I dont know how you have to access the data in the files, but perhaps the interface of mmfile is good enough for you! christian
Re: implicit casting from primitive type
On Mon, 29 Aug 2011 21:33:13 +0200, Mariusz Gliwiński wrote:
Hello,
this will be easy question. I defined attributes, that are taking my
custom structures as attributes. Then, I'd like to add implicit
conversion to this structures from primitive types, such as: code
some.attribute = [1, 2, 3]; // i'd like to do that some.attribute =
MyStruct(1, 2, 3); // now it's like that /code
opCast can be used only to casting FROM my type, but not TO... Was that
in a book?
Thanks,
Mariusz Gliwiński
To solve it for this specific case, you can overload attribute() to take
int[]:
import std.exception;
struct MyStruct
{
int i;
int j;
int k;
}
struct CustomStruct
{
MyStruct ms;
@property void attribute(int[] args)
{
enforce(args.length == 3);
ms = MyStruct(args[0], args[1], args[2]);
}
}
void main()
{
auto some = CustomStruct();
some.attribute = [ 1, 2, 3 ];
}
Ali
Re: implicit casting from primitive type
Ali Çehreli wrote: To solve it for this specific case, you can overload attribute() to take int[]: I know, but i don't really want to. Too many overrides or templates, but i'll consider it if wont find any better solution. Thanks, Mariusz Gliwiński
struct opEquals does not work with parameter of same type - bug or feature?
I am trying to build a struct with equality testing, using this code:
struct Foo
{
const bool opEquals(Foo f)
{
return true;
}
}
This gives me the error that the parameter should be of type ref const Foo.
Fine.
struct Foo
{
const bool opEquals(ref const Foo f)
{
return true;
}
}
This, however, does not work with code like:
Foo bar()
{
return Foo();
}
assert(Foo() == bar());
function Foo.opEquals(ref const const(Foo) f) const is not callable using
argument types (Foo) and bar() is not an lvalue.
How can I do this?
How do I pass multidimensional static arrays to functions expecting dynamic arrays?
Take a look:
void main()
{
int[2] single;
// foo(single); // no
foo(single[]); // int[2][] slice, ok
int[2][2] multi;
// bar(multi); // int[2][2] no
// bar(multi[]); // int[2][] slice, no
// bar(multi[][]); // int[2][] slice, no
}
void foo(int[] value) {}
void bar(int[][] value) {}
I can easily slice a one-dimensional static array, but I can only
slice a single dimension. So how do I pass a multidimensional static
array to a function expecting a multidimensional dynamic array?
Re: How do I pass multidimensional static arrays to functions expecting dynamic arrays?
On 08/30/2011 01:29 AM, Andrej Mitrovic wrote:
Take a look:
void main()
{
int[2] single;
// foo(single); // no
foo(single[]); // int[2][] slice, ok
int[2][2] multi;
// bar(multi); // int[2][2] no
// bar(multi[]); // int[2][] slice, no
// bar(multi[][]); // int[2][] slice, no
}
void foo(int[] value) {}
void bar(int[][] value) {}
I can easily slice a one-dimensional static array, but I can only
slice a single dimension. So how do I pass a multidimensional static
array to a function expecting a multidimensional dynamic array?
D does not have multidimensional dynamic arrays.
To solve your problem, you have to manually create an array of 1D-slices:
Like this:
bar(array(map!((int[] a){return a;})(multi[])));
Or like this:
int[][] arg=new int[][](2);
foreach(i,ref x;arg) x=multi[i][];
bar(arg);
Re: struct opEquals does not work with parameter of same type - bug or feature?
On Monday, August 29, 2011 22:41:26 Sean Eskapp wrote:
I am trying to build a struct with equality testing, using this code:
struct Foo
{
const bool opEquals(Foo f)
{
return true;
}
}
This gives me the error that the parameter should be of type ref const
Foo. Fine.
struct Foo
{
const bool opEquals(ref const Foo f)
{
return true;
}
}
This, however, does not work with code like:
Foo bar()
{
return Foo();
}
assert(Foo() == bar());
function Foo.opEquals(ref const const(Foo) f) const is not callable using
argument types (Foo) and bar() is not an lvalue.
How can I do this?
http://d.puremagic.com/issues/show_bug.cgi?id=3659
http://stackoverflow.com/questions/6986175/const-ref-and-rvalue-in-d
- Jonathan M Davis
Re: struct opEquals does not work with parameter of same type - bug or feature?
== Quote from Jonathan M Davis (jmdavisp...@gmx.com)'s article
On Monday, August 29, 2011 22:41:26 Sean Eskapp wrote:
I am trying to build a struct with equality testing, using this code:
struct Foo
{
const bool opEquals(Foo f)
{
return true;
}
}
This gives me the error that the parameter should be of type ref const
Foo. Fine.
struct Foo
{
const bool opEquals(ref const Foo f)
{
return true;
}
}
This, however, does not work with code like:
Foo bar()
{
return Foo();
}
assert(Foo() == bar());
function Foo.opEquals(ref const const(Foo) f) const is not callable using
argument types (Foo) and bar() is not an lvalue.
How can I do this?
http://d.puremagic.com/issues/show_bug.cgi?id=3659
http://stackoverflow.com/questions/6986175/const-ref-and-rvalue-in-d
- Jonathan M Davis
Ah, thanks!
Re: How do I pass multidimensional static arrays to functions expecting
Timon Gehr:
bar(array(map!((int[] a){return a;})(multi[])));
Simpler:
bar( array(map!q{ a[] }(multi[])) );
Simpler still when we'll get amap:
bar( amap!q{ a[] }(multi[]) );
Bye,
bearophile
Re: How do I pass multidimensional static arrays to functions expecting dynamic arrays?
Right, but I was just trying to temporarily avoid GC allocation so I've used a static array instead of a dynamic ones. Also, I don't know of another term that is used to describe a int[][] array, other than multidimensional. Anyway this works fine for me (int wasn't a requirement in this case): void foo(T)(T val) if (isArray!T) void bar(T)(T val) if (isArray!T isArray!(ElementType!T))
Re: How do I pass multidimensional static arrays to functions expecting dynamic arrays?
Hey btw, do you think we could use this in Phobos?
template BaseElementType(R)
{
static if (isArray!(ElementType!R))
alias BaseElementType!(ElementType!R) BaseElementType;
else static if (is(typeof({return R.init.front();}()) T))
alias T BaseElementType;
else
alias void BaseElementType;
}
assert(is(BaseElementType!(int[][]) == int));
Maybe a better name is RootElementType. Not too sure.
Re: How do I pass multidimensional static arrays to functions expecting dynamic arrays?
On Tuesday, August 30, 2011 03:43:39 Andrej Mitrovic wrote: Right, but I was just trying to temporarily avoid GC allocation so I've used a static array instead of a dynamic ones. Also, I don't know of another term that is used to describe a int[][] array, other than multidimensional. It _is_ multi-dimensional. I'm not quite sure why Timon is saying that it isn't. Ultimately though, a multi-dimensional dynamic array is an array of arrays (or array of arrays of arrays of ...). When slicing it, you get the a portion of the outermost array. If you index that, you can get at the inner arrays to slice those if you want to, but the inner arrays know nothing about the outer arrays, and actually taking a slice of the whole where you get the outer array and some portion of the inner arrays would require creating a new array, so you can't really do it. I can't really think of a clean way of explaining it without diagrams, and even then it's a bit of a pain, but with a slice, it's only a matter of adjusting its ptr and length properties. If you want a multi-dimensional slice, you'd need to adjust the ptr and length properties of the arrays that the slice contained, and you can't do that without affecting the original arrays unless you copy them. So, ultimately, you need to construct a new multi-dimensional array with the pieces that you want if you want a multi- dimensional slice. - Jonathan M Davis
