Re: D Beginner Trying Manual Memory Management
I see, thanks! :) I've started liking structs more and more recently as well and been pondering on how to convert a class-based code that looks like this (only the base class has any data): it's hard to tell by brief description. but having multiple inheritance immediately rings an alarm ring for me. something is very-very-very wrong if you need to have a winged whale. ;-) A real-world example: http://www.hdfgroup.org/HDF5/doc/cpplus_RM/hierarchy.html H5::File is both an H5::Location and H5::CommonFG (but not an H5::Object) H5::Group is both an H5::Object (subclass of H5::Location) and H5::CommonFG H5::Dataset is an H5::Object i see something named CommonFG here, which seems to good thing to move out of hierarchy altogether. bwah, i don't even sure that given hierarchy is good for D. C++ has no UFCS, and it's incredibly hard to check if some entity has some methods/properties in C++, so they have no other choice than to work around that limitations. it may be worthful to redesign the whole thing for D, exploiting D shiny UFCS and metaprogramming features. and, maybe, moving some things to interfaces too. I just finished reading aldanor's blog, so I know he is slightly allergic to naked functions and prefers classes ;) With Ketmar, I very much agree (predominantly as a user of HDF5 and less so as an inexperienced D programmr writing a wrapper for it). It's a pain to figure out just how to do simple things until you know the H5 library. You have to create an object for file permissions before you even get started, then similarly for the data series (datasets) within, another for the dimensions of the array, etc etc - that doesn't fit with the intrinsic nature of the domain. There is a more general question of bindings/wrappers - preserve the original structure and naming so existing code can be ported, or write a wrapper that makes it easy for the user to accomplish his objectives. It seems like for the bindings preserving the library structure is fine, but for the wrapper one might as well make things easy. Eg here https://gist.github.com/Laeeth/9637233db41a11a9d1f4 line 146. (sorry for duplication and messiness of code, which I don't claim to be perfectly written - I wanted to try something quickly and have not yet tidied up). So rather than navigate the Byzantine hierarchy, one can just do something like this (which will take a struct of PriceBar - date,open,high,low,close - and put it in your desired dataset and file, appending or overwriting as you prefer). dumpDataSpaceVector!PriceBar(file,ticker,array(priceBars[ticker]),DumpMode.truncate); which is closer to h5py in Python. (It uses reflection to figure out the contents of a non-nested struct, but won't yet cope with arrays and nested structs inside). And of course a full wrapper might be a bit more complicated, but I truly think one can do better than mapping the HDF5 hierarchy one for one. Laeeth.
reinterpret array
Does the following construct hold water?
version(LittleEndian)
{
/// interpret an array of one type as an array of a different
type.
/// if the array has odd length, the highest elements are
/// not accessible, at worst an empty slice is returned
inout ref T[] arrayOf(T, V: U[])(inout ref V a)
pure @safe nothrow
if(isUnsigned!T isUnsigned!U)
{
return (cast(T*)a.ptr)[0 .. a.length * U.sizeof / T.sizeof];
}
unittest
{
ubyte a[5] = { 1, 2, 3, 4, 5 };
auto b = a.arrayOf!uint;
assert(typeof(b) == uint[]);
assert(b.length == 1);
assert(b[0] == 0x04030201);
assert(b[0] == a[0]); // b is a slice of a
b[0] = 0x0a0b0c0d; // this will change a
assert(a == { 13, 12, 11, 10, 5 });
ushort c[2] = { 257, 512 };
auto d = c.arrayOf!ubyte;
assert(d.length == 4);
assert(d[0] == 1);
assert(d[1] == 1);
assert(d[2] == 0);
assert(d[3] == 2);
}
}
I assume taking a slice of a pointer uses the GC, so this cannot
be @nogc, am I right? And I assume it is @save, because if I
would increase the length of the returned value, the GC will
automatically re-allocate, but then of course the adress is no
more the same, yes?
Re: D Beginner Trying Manual Memory Management
On Tue, 13 Jan 2015 17:08:37 + Laeeth Isharc via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: I just finished reading aldanor's blog, so I know he is slightly allergic to naked functions and prefers classes ;) that's due to absense of modules in C/C++. and namespaces aren't of big help here too. and, of course, due to missing UFCS, that prevents nice `obj.func()` for free functions. ;-) signature.asc Description: PGP signature
Re: A naive attempt at a refcounted class proxy
On Tue, 13 Jan 2015 18:12:44 +
aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
wrote:
On Tuesday, 13 January 2015 at 16:43:09 UTC, ketmar via
Digitalmars-d-learn wrote:
On Tue, 13 Jan 2015 16:17:51 +
aldanor via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
This discussion:
http://forum.dlang.org/thread/bqtcdpsopxmnfbjyr...@forum.dlang.org
-- led me wondering if it would be possible to create some
crippled version of a class proxy that is based on RefCounted
and came up with something like this:
struct Box(T) if (is(T == class)) {
@disable this();
this(Args...)(Args args) {
_payload._refCounted.initialize(new T(args));
}
private {
struct _Box(T) {
private T _instance;
~this() {
destroy(_instance);
}
}
RefCounted!(_Box!T) _payload;
}
~this() {
}
auto opDispatch(string name, Args...)(Args args) {
return
mixin(_payload._instance.%s(args).format(name));
}
}
which lets you create Box!SomeClass(args) and it will be
refcounted unless you escape references and do other weird
stuff.
It actually sort of seems to work at first glance, at least it
seems like it does... But with my D experience being fairly
limited I wonder what the potential pitfalls would be?
Full source code with example and stdout:
https://gist.github.com/aldanor/d5fb5e45ddf3dd2cb642
it's not that hard to make a boxed class. what is really hard
is to
make functions that expects the class itself to accept it's
boxed
variant too and behave correctly with it.
either you have to unbox it (and then hope that it will not
leak), or
write two set of functions, for real class and for boxed one.
and
then you may want to inherit from your class and pass that
inherited
class to one of the functions... and now you have three sets.
and so
on...
as structs can't be inherited, there is no such problem for
structs.
That's completely valid. Where it would work though, I think, is
if all classes are private/package and only expect/return boxed
classes and never the references. This way you sort of get
multiple inheritance (for the internal implementation) without
polymorphism, but with value semantics and ref counting for the
outward interface.
and then you can go with structures in the first place, i think.
remember that you have that k00l `alias this` trick for them!
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Re: idiomatic D: what to use instead of pointers in constructing a tree data structure?
On Wednesday, 7 January 2015 at 14:59:58 UTC, H. S. Teoh via Digitalmars-d-learn wrote: On Wed, Jan 07, 2015 at 02:52:51PM +, Laeeth Isharc via Digitalmars-d-learn wrote: Another schoolboy question. Suppose I am constructing a tree (in this case it is an AST). In C I would have a pointer for the child to find the parent, and an array or linked list of pointers to find the children from the parent. Obviously, I could still use pointers, but that would not be idiomatic. Not true. If you're using a tree structure, you *should* use pointers. Unless you're using classes, which are by-reference, in which case you can just use the class as-is. :-) --T The GC is allowed to move structs around, as I undestand it. Under what circumstances do I get into trouble having a pointer to them?
Re: reinterpret array
On Tuesday, 13 January 2015 at 17:12:42 UTC, Adam D. Ruppe wrote: On Tuesday, 13 January 2015 at 17:09:32 UTC, Dominikus Dittes Scherkl wrote: I assume taking a slice of a pointer uses the GC, so this cannot be @nogc, am I right? Nope, slicing never allocates, it just takes an address and length. If you append to a slice or increase the length though, the GC might reallocate it. Cool. So I can make the above even @nogc ? Great.
Re: reinterpret array
On Tuesday, 13 January 2015 at 17:09:32 UTC, Dominikus Dittes Scherkl wrote: I assume taking a slice of a pointer uses the GC, so this cannot be @nogc, am I right? Nope, slicing never allocates, it just takes an address and length. If you append to a slice or increase the length though, the GC might reallocate it.
Re: idiomatic D: what to use instead of pointers in constructing a tree data structure?
On Tuesday, 13 January 2015 at 17:19:42 UTC, Laeeth Isharc wrote: The GC is allowed to move structs around, as I undestand it. Under what circumstances do I get into trouble having a pointer to them? None, a GC that moves structs around must update every pointer afterwards and as far as I know, the standard GC doesn't do that (moving things around). You may not have a pointer inside a struct that points to the struct itself. This allows the compiler to elide some copies.
Re: A naive attempt at a refcounted class proxy
On Tuesday, 13 January 2015 at 16:43:09 UTC, ketmar via
Digitalmars-d-learn wrote:
On Tue, 13 Jan 2015 16:17:51 +
aldanor via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
This discussion:
http://forum.dlang.org/thread/bqtcdpsopxmnfbjyr...@forum.dlang.org
-- led me wondering if it would be possible to create some
crippled version of a class proxy that is based on RefCounted
and came up with something like this:
struct Box(T) if (is(T == class)) {
@disable this();
this(Args...)(Args args) {
_payload._refCounted.initialize(new T(args));
}
private {
struct _Box(T) {
private T _instance;
~this() {
destroy(_instance);
}
}
RefCounted!(_Box!T) _payload;
}
~this() {
}
auto opDispatch(string name, Args...)(Args args) {
return
mixin(_payload._instance.%s(args).format(name));
}
}
which lets you create Box!SomeClass(args) and it will be
refcounted unless you escape references and do other weird
stuff.
It actually sort of seems to work at first glance, at least it
seems like it does... But with my D experience being fairly
limited I wonder what the potential pitfalls would be?
Full source code with example and stdout:
https://gist.github.com/aldanor/d5fb5e45ddf3dd2cb642
it's not that hard to make a boxed class. what is really hard
is to
make functions that expects the class itself to accept it's
boxed
variant too and behave correctly with it.
either you have to unbox it (and then hope that it will not
leak), or
write two set of functions, for real class and for boxed one.
and
then you may want to inherit from your class and pass that
inherited
class to one of the functions... and now you have three sets.
and so
on...
as structs can't be inherited, there is no such problem for
structs.
That's completely valid. Where it would work though, I think, is
if all classes are private/package and only expect/return boxed
classes and never the references. This way you sort of get
multiple inheritance (for the internal implementation) without
polymorphism, but with value semantics and ref counting for the
outward interface.
Re: A naive attempt at a refcounted class proxy
On Tuesday, 13 January 2015 at 18:12:45 UTC, aldanor wrote:
On Tuesday, 13 January 2015 at 16:43:09 UTC, ketmar via
Digitalmars-d-learn wrote:
On Tue, 13 Jan 2015 16:17:51 +
aldanor via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
This discussion:
http://forum.dlang.org/thread/bqtcdpsopxmnfbjyr...@forum.dlang.org
-- led me wondering if it would be possible to create some
crippled version of a class proxy that is based on RefCounted
and came up with something like this:
struct Box(T) if (is(T == class)) {
@disable this();
this(Args...)(Args args) {
_payload._refCounted.initialize(new T(args));
}
private {
struct _Box(T) {
private T _instance;
~this() {
destroy(_instance);
}
}
RefCounted!(_Box!T) _payload;
}
~this() {
}
auto opDispatch(string name, Args...)(Args args) {
return
mixin(_payload._instance.%s(args).format(name));
}
}
which lets you create Box!SomeClass(args) and it will be
refcounted unless you escape references and do other weird
stuff.
It actually sort of seems to work at first glance, at least
it seems like it does... But with my D experience being
fairly limited I wonder what the potential pitfalls would be?
Full source code with example and stdout:
https://gist.github.com/aldanor/d5fb5e45ddf3dd2cb642
it's not that hard to make a boxed class. what is really hard
is to
make functions that expects the class itself to accept it's
boxed
variant too and behave correctly with it.
either you have to unbox it (and then hope that it will not
leak), or
write two set of functions, for real class and for boxed
one. and
then you may want to inherit from your class and pass that
inherited
class to one of the functions... and now you have three sets.
and so
on...
as structs can't be inherited, there is no such problem for
structs.
That's completely valid. Where it would work though, I think,
is if all classes are private/package and only expect/return
boxed classes and never the references. This way you sort of
get multiple inheritance (for the internal implementation)
without polymorphism, but with value semantics and ref counting
for the outward interface.
// thanks ketmar for answering another one of my stupid questions
on n.g. :)
Re: A naive attempt at a refcounted class proxy
On Tue, 13 Jan 2015 18:14:40 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: // thanks ketmar for answering another one of my stupid questions on n.g. :) ah, 'cmon, your questions aren't stupid at all! ;-) signature.asc Description: PGP signature
Re: reinterpret array
On Tue, 13 Jan 2015 17:09:31 +
Dominikus Dittes Scherkl via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com wrote:
/// interpret an array of one type as an array of a different
type.
may i point you to this?
import std.stdio;
void main () {
ubyte[] a = [42,0,0,0, 155,2,0,0];
auto b = cast(uint[])a;
writeln(b); // [42, 667]
}
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Re: A naive attempt at a refcounted class proxy
On Tue, 13 Jan 2015 18:36:15 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: On Tuesday, 13 January 2015 at 18:19:42 UTC, ketmar via Digitalmars-d-learn wrote: and then you can go with structures in the first place, i think. remember that you have that k00l `alias this` trick for them! Which doesn't always help in case of multiple inheritance :( e.g. the blasted hdf c++ class hierarchy example. multiple `alias this` may help here... to some extent. ;-) signature.asc Description: PGP signature
Re: D Beginner Trying Manual Memory Management
On Tue, 13 Jan 2015 18:35:15 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: I guess two of my gripes with UFCS is (a) you really have to use public imports in the modules where the target types are defined so you bring all the symbols in whether you want it or not (b) you lose access to private members because it's not the same module anymore (correct me if I'm wrong?). Plus, you need to decorate every single free function with a template constraint. you can make a package and set protection to `package` instead of `private`, so your function will still be able to access internal fields, but package users will not. this feature is often missed by the people who are used to `public`/`protected`/`private` triad. signature.asc Description: PGP signature
Re: reinterpret array
On Tuesday, 13 January 2015 at 18:25:38 UTC, ketmar via
Digitalmars-d-learn wrote:
On Tue, 13 Jan 2015 17:09:31 +
Dominikus Dittes Scherkl via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com wrote:
/// interpret an array of one type as an array of a
different type.
may i point you to this?
import std.stdio;
void main () {
ubyte[] a = [42,0,0,0, 155,2,0,0];
auto b = cast(uint[])a;
writeln(b); // [42, 667]
}
I see. So this function is completely superfluous :-/
Good to know.
So if I have a function that allowes to do this:
uint a;
a.bit[16] = true;
writeln(a); // 65536
Is it also already available?
Because I somewhat hate it that with D I can create great stuff,
but it is not necessary because D already has something much
cooler...
Re: D Beginner Trying Manual Memory Management
On Tuesday, 13 January 2015 at 17:08:38 UTC, Laeeth Isharc wrote:
I see, thanks! :) I've started liking structs more and
more recently as well and been pondering on how to convert
a class-based code that looks like this (only the base
class has any data):
it's hard to tell by brief description. but having multiple
inheritance
immediately rings an alarm ring for me. something is
very-very-very
wrong if you need to have a winged whale. ;-)
A real-world example:
http://www.hdfgroup.org/HDF5/doc/cpplus_RM/hierarchy.html
H5::File is both an H5::Location and H5::CommonFG (but not an
H5::Object)
H5::Group is both an H5::Object (subclass of H5::Location)
and H5::CommonFG
H5::Dataset is an H5::Object
i see something named CommonFG here, which seems to good
thing to
move out of hierarchy altogether.
bwah, i don't even sure that given hierarchy is good for D.
C++ has no
UFCS, and it's incredibly hard to check if some entity has some
methods/properties in C++, so they have no other choice than
to work
around that limitations. it may be worthful to redesign the
whole thing
for D, exploiting D shiny UFCS and metaprogramming features.
and,
maybe, moving some things to interfaces too.
I just finished reading aldanor's blog, so I know he is
slightly allergic to naked functions and prefers classes ;)
With Ketmar, I very much agree (predominantly as a user of HDF5
and less so as an inexperienced D programmr writing a wrapper
for it). It's a pain to figure out just how to do simple
things until you know the H5 library. You have to create an
object for file permissions before you even get started, then
similarly for the data series (datasets) within, another for
the dimensions of the array, etc etc - that doesn't fit with
the intrinsic nature of the domain.
There is a more general question of bindings/wrappers -
preserve the original structure and naming so existing code can
be ported, or write a wrapper that makes it easy for the user
to accomplish his objectives. It seems like for the bindings
preserving the library structure is fine, but for the wrapper
one might as well make things easy.
Eg here https://gist.github.com/Laeeth/9637233db41a11a9d1f4
line 146. (sorry for duplication and messiness of code, which
I don't claim to be perfectly written - I wanted to try
something quickly and have not yet tidied up).
So rather than navigate the Byzantine hierarchy, one can just
do something like this (which will take a struct of PriceBar -
date,open,high,low,close - and put it in your desired dataset
and file, appending or overwriting as you prefer).
dumpDataSpaceVector!PriceBar(file,ticker,array(priceBars[ticker]),DumpMode.truncate);
which is closer to h5py in Python. (It uses reflection to
figure out the contents of a non-nested struct, but won't yet
cope with arrays and nested structs inside). And of course a
full wrapper might be a bit more complicated, but I truly think
one can do better than mapping the HDF5 hierarchy one for one.
Laeeth.
In the hierarchy example above (c++ hdf hierarchy link), by using
UFCS to implement the shared methods (which are achieved by
multiple inheritance in the c++ counterpart) did you mean
something like this?
// id.d
struct ID { int id; ... }
// location.d
struct Location { ID _id; alias _id this; ... }
// file.d
public import commonfg; // ugh
struct File { Location _location; alias _location this; ... }
// group.d
public import commonfg;
struct File { Location _location; alias _location this; ... }
// commonfg.d { ... }
enum isContainer(T) = is(T: File) || is(T : Group);
auto method1(T)(T obj, args) if (isContainer!T) { ... }
auto method2(T)(T obj, args) if (isContainer!T) { ... }
I guess two of my gripes with UFCS is (a) you really have to use
public imports in the modules where the target types are defined
so you bring all the symbols in whether you want it or not (b)
you lose access to private members because it's not the same
module anymore (correct me if I'm wrong?). Plus, you need to
decorate every single free function with a template constraint.
// another hdf-specific thing here but a good example in general
is that some functions return you an id for an object which is
one of the location subtypes (e.g. it could be a File or could be
a Group depending on run-time conditions), so it kind of feels
natural to use polymorphism and classes for that, but what would
you do with the struct approach? The only thing that comes to
mind is Variant, but it's quite meh to use in practice.
Re: A naive attempt at a refcounted class proxy
On Tuesday, 13 January 2015 at 18:19:42 UTC, ketmar via Digitalmars-d-learn wrote: and then you can go with structures in the first place, i think. remember that you have that k00l `alias this` trick for them! Which doesn't always help in case of multiple inheritance :( e.g. the blasted hdf c++ class hierarchy example.
Re: reinterpret array
On Tuesday, 13 January 2015 at 20:00:57 UTC, Dominikus Dittes Scherkl wrote: So if I have a function that allowes to do this: uint a; a.bit[16] = true; writeln(a); // 65536 Is it also already available? a |= 1 16;
Re: Pointers and offsets
On 1/14/2015 10:17 AM, Bauss wrote:
On Wednesday, 14 January 2015 at 01:16:54 UTC, Bauss wrote:
Is it possible to access a pointer by its offsets.
Ex. write a 32bit integer to a byte pointer at ex. offset 4.
To give an example in C# you can do this:
fixed (byte* Packet = Buffer) // Buffer would be a byte array
And then to set the value of a specific offset
*((TYPE*)(Packet + OFFSET))
Where TYPE could be replaced by ex. uint and OFFSET by 4
I tried to look here:
http://dlang.org/arrays.html
But couldn't seem to find anything like it.
Can't seem to edit OP so at:
The forum is a web interface to a newsgroup, which also has a mailing
list interface. So no, no editing.
*((TYPE*)(Packet + OFFSET))
It should be:
*((TYPE*)(Packet + OFFSET)) = VALUE;
VALUE has to be of the same type as TYPE of course.
void main()
{
ubyte[16] bytes;
for( int i=0; i4; ++i )
{
*(cast( int* )( bytes.ptr + (i*4))) = i;
}
import std.stdio : writeln;
writeln( cast( int[] )bytes );
}
Re: Map Lambda with Side-Effects
Is it possible to - detect that a lambda is has-side-effects and that - the map hasn't been used? Thing is: I'm regularly doing that on purpose. Actually, isn't your closure even weakly pure in your example, because arr is part of the closure and thus an argument to it.
Re: Pointers and offsets
On Wednesday, 14 January 2015 at 01:16:54 UTC, Bauss wrote: Is it possible to access a pointer by its offsets. Ex. write a 32bit integer to a byte pointer at ex. offset 4. To give an example in C# you can do this: fixed (byte* Packet = Buffer) // Buffer would be a byte array And then to set the value of a specific offset *((TYPE*)(Packet + OFFSET)) Where TYPE could be replaced by ex. uint and OFFSET by 4 I tried to look here: http://dlang.org/arrays.html But couldn't seem to find anything like it. Can't seem to edit OP so at: *((TYPE*)(Packet + OFFSET)) It should be: *((TYPE*)(Packet + OFFSET)) = VALUE; VALUE has to be of the same type as TYPE of course.
Pointers and offsets
Is it possible to access a pointer by its offsets. Ex. write a 32bit integer to a byte pointer at ex. offset 4. To give an example in C# you can do this: fixed (byte* Packet = Buffer) // Buffer would be a byte array And then to set the value of a specific offset *((TYPE*)(Packet + OFFSET)) Where TYPE could be replaced by ex. uint and OFFSET by 4 I tried to look here: http://dlang.org/arrays.html But couldn't seem to find anything like it.
Re: D Beginner Trying Manual Memory Management
On Mon, 12 Jan 2015 22:07:13 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: I see, thanks! :) I've started liking structs more and more recently as well and been pondering on how to convert a class-based code that looks like this (only the base class has any data): it's hard to tell by brief description. but having multiple inheritance immediately rings an alarm ring for me. something is very-very-very wrong if you need to have a winged whale. ;-) signature.asc Description: PGP signature
Re: D Beginner Trying Manual Memory Management
On Mon, 12 Jan 2015 23:06:16 + jmh530 via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: I had seen some stuff on alias thing, but I hadn't bothered to try to understand it until now. If I'm understanding the first example a href=http://dlang.org/class.html#AliasThis;here/a, alias this let's you refer to x in s by writing either s.x (as normally) or just s. That didn't seem that interesting, but then I found a href=http://3d.benjamin-thaut.de/?p=90;example/a where they alias this'ed a struct method. That's pretty interesting. there is nice page by p0nce and it shows nice and simple `alias this` trick usage: http://p0nce.github.io/d-idioms/#Extending-a-struct-with-alias-this and i have stream.d module in my IV package ( http://repo.or.cz/w/iv.d.git/tree ), which works with i/o streams by testing if passed struct/class has necessary methods (`isReadable!`, `isWriteable!`, `isSeekable!`, etc. signature.asc Description: PGP signature
Re: D Beginner Trying Manual Memory Management
On Mon, 12 Jan 2015 22:07:13 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: I see, thanks! :) I've started liking structs more and more recently as well and been pondering on how to convert a class-based code that looks like this (only the base class has any data): p.s. can't you convert most of that to free functions? thanks to UFCS you'll be able to use them with `obj.func` notation. and by either defining `package` protection for class fields, or simply writing that functions in the same module they will have access to internal object stuff. and if you can return `obj` from each function, you can go with templates and chaining. ;-) signature.asc Description: PGP signature
Re: Endless static this call when used a thread in it
V Tue, 13 Jan 2015 13:53:09 +
tcak via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
napsáno:
I have written the following code:
test.d
==
import core.thread;
import std.stdio;
void threadFunc(){
writeln(Thread func);
}
public static this(){
auto t = new Thread( threadFunc );
t.start();
writeln(Static init);
}
void main(){
writeln(End of main);
}
run
==
rdmd test.d
result
==
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Sta...
Is this normal, what's happening?
try
shared static this(){
...
instead of
public static this(){
Re: Endless static this call when used a thread in it
On Tuesday, 13 January 2015 at 13:53:11 UTC, tcak wrote:
I have written the following code:
test.d
==
import core.thread;
import std.stdio;
void threadFunc(){
writeln(Thread func);
}
public static this(){
auto t = new Thread( threadFunc );
t.start();
writeln(Static init);
}
void main(){
writeln(End of main);
}
run
==
rdmd test.d
result
==
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Sta...
Is this normal, what's happening?
When I defined static init with shared
public shared static this()
it works normal now. But it doesn't explain above issue. What's
the relation between a new thread and a module's initialiser?
Re: Endless static this call when used a thread in it
On Tue, 13 Jan 2015 13:56:05 + tcak via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: it works normal now. But it doesn't explain above issue. What's the relation between a new thread and a module's initialiser? yes. signature.asc Description: PGP signature
Re: Endless static this call when used a thread in it
V Tue, 13 Jan 2015 13:56:05 +
tcak via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
napsáno:
On Tuesday, 13 January 2015 at 13:53:11 UTC, tcak wrote:
I have written the following code:
test.d
==
import core.thread;
import std.stdio;
void threadFunc(){
writeln(Thread func);
}
public static this(){
auto t = new Thread( threadFunc );
t.start();
writeln(Static init);
}
void main(){
writeln(End of main);
}
run
==
rdmd test.d
result
==
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Sta...
Is this normal, what's happening?
When I defined static init with shared
public shared static this()
it works normal now. But it doesn't explain above issue. What's
the relation between a new thread and a module's initialiser?
I am not sure but my guess is
static this needs to be called before anything else in module so when
you try call threadFunc it looks if static this has been called and
finished which is not true so it call it again
Re: Endless static this call when used a thread in it
On Tuesday, 13 January 2015 at 14:02:45 UTC, Daniel Kozák via
Digitalmars-d-learn wrote:
V Tue, 13 Jan 2015 13:56:05 +
tcak via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
napsáno:
On Tuesday, 13 January 2015 at 13:53:11 UTC, tcak wrote:
I have written the following code:
test.d
==
import core.thread;
import std.stdio;
void threadFunc(){
writeln(Thread func);
}
public static this(){
auto t = new Thread( threadFunc );
t.start();
writeln(Static init);
}
void main(){
writeln(End of main);
}
run
==
rdmd test.d
result
==
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Sta...
Is this normal, what's happening?
When I defined static init with shared
public shared static this()
it works normal now. But it doesn't explain above issue.
What's the relation between a new thread and a module's
initialiser?
I am not sure but my guess is
static this needs to be called before anything else in module
so when
you try call threadFunc it looks if static this has been called
and
finished which is not true so it call it again
And here is better explanation
http://dlang.org/module.html#staticorder
Static constructors are code that gets executed to initialize a
module or a class before the main() function gets called.
...
Static constructors and static destructors run on thread local
data, and are run whenever threads are created or destroyed.
Re: Read from stdin without blocking
The operating system does line buffering, so you'll need to turn that off. The function is tcssetattr() on Posix and SetConsoleMode on Windows. My terminal.d does this in struct ctors and dtors: https://github.com/adamdruppe/arsd/blob/master/terminal.d example usage: http://arsdnet.net/dcode/book/chapter_12/07/input.d The RealTimeConsoleInput struct turns off buffering and has functions like getch() and kbhit() to fetch individual characters from it. That's not quite the same as getting everything that's available, but might be useful to you. Most efficient way I think though is to turn off buffering with the OS calls, then you can set stdin to be nonblocking and read chunks off it with ordinary read() or ReadFile calls.
Re: Map Lambda with Side-Effects
On Tuesday, 13 January 2015 at 10:21:12 UTC, Tobias Pankrath wrote: On Tuesday, 13 January 2015 at 10:06:26 UTC, bearophile wrote: Nordlöw: Has there been any discussions on making map require pure functions now that we have each? Perhaps I'd like Phobos map and filter to be annotated with pure and to have a template constraint that requires their mapping/filtering functions to be strongly pure. Bye, bearophile Please not. It should be obviously documented that the number of applications of the function is not limited to once-per-element and that evaluation doesn't necessarily happen in-order. I forget and am re-reminded of this once every few months, despite how central it is to ranges in general. It can still be useful to use impure functions with it though, as long as you consider what is actually going on.
Re: Accessing class with module name as Java's
Ah, I just re-read your OP. Your already at this point :)
Since everybody has understood the problem, and nobody could have
come up with a solution yet, my idea is that:
HttpSocketConnectionRequest.d
=
module net.http.HttpSocketConnectionRequest;
module class HttpSocketConnectionRequest{}
If compiler allowed module keyword to be used as an attribute
for ONLY ONE class or struct definition in the module as above,
module's name could be used as you were to be pointing to class
directly.
This would let us (and Phobos developers) to be able to separate
code files into multiple files much easily, and solve my problem
as well :).
Re: Map Lambda with Side-Effects
On Tue, 13 Jan 2015 10:06:25 + bearophile via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: Nordlöw: Has there been any discussions on making map require pure functions now that we have each? Perhaps I'd like Phobos map and filter to be annotated with pure and to have a template constraint that requires their mapping/filtering functions to be strongly pure. that will effectively rule out any usage of some global vars or other external state, turning it into either unnecessary mess, or unusable theoretical crap. what i think should be written in big red letters in docs is there is no guarantees about how many times labmda will be called, with which args and in which order. so if someone wants to shoot in his foot, he can ignore that warning and do crazy shooting. signature.asc Description: PGP signature
Re: Map Lambda with Side-Effects
Nordlöw: Has there been any discussions on making map require pure functions now that we have each? Perhaps I'd like Phobos map and filter to be annotated with pure and to have a template constraint that requires their mapping/filtering functions to be strongly pure. Bye, bearophile
Re: Map Lambda with Side-Effects
On Tue, 13 Jan 2015 11:26:01 + bearophile via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: ketmar: that will effectively rule out any usage of some global vars or other external state, turning it into either unnecessary mess, or unusable theoretical crap. Unusable theoretical crap is better than the current trap :-) in no way. this just turns Phobos into the same unusable crap, removing the whole sense of having good standard library. We hare pure in D, but still we have not grown up to actually use it in Phobos, for higher order functions, or parallelism. let an user choose if he wants pure or impure HOF args. just make a big warning in documentation about unpredictability of HOFs with side-effects and this will be enough, i believe. signature.asc Description: PGP signature
Re: Accessing class with module name as Java's
Have the following directory structure? ~/testModule$ find . -print . ./net ./net/http_.d# ** ./net/http ./net/http/Mod1.d ./net/http/Mod2.d ./main.d ** I put the _ here to make it seperate from the net/http directory. Probably, a better solution exists, this was hacked together quickly :) In http_.d have: module net.http_; // again, a better solution surely exists public import net.http.Mod1; public import net.http.Mod2; Then in your main have import net.http_; You can then use whatever's in Mod1 and Mod2 modules. In your case, Mod1/Mod2 will be like HTTPConnectionRequest/HTTPConnectionResponse and will only contain a single class. This works for me. You can also go a little further and have renamed imports. Something like: public import Renamed = net.http.Mod2; Then in main.d call it with: Renamed.Mod2 mod2 = new renamed.Mod2; Feels just like Java :)
Re: Map Lambda with Side-Effects
On Tuesday, 13 January 2015 at 10:06:26 UTC, bearophile wrote: Nordlöw: Has there been any discussions on making map require pure functions now that we have each? Perhaps I'd like Phobos map and filter to be annotated with pure and to have a template constraint that requires their mapping/filtering functions to be strongly pure. Bye, bearophile Please not.
Re: Map Lambda with Side-Effects
ketmar: that will effectively rule out any usage of some global vars or other external state, turning it into either unnecessary mess, or unusable theoretical crap. Unusable theoretical crap is better than the current trap :-) We hare pure in D, but still we have not grown up to actually use it in Phobos, for higher order functions, or parallelism. Bye, bearophile
Re: Accessing class with module name as Java's
On Tuesday, 13 January 2015 at 09:22:04 UTC, Colin wrote: Have the following directory structure? ~/testModule$ find . -print . ./net ./net/http_.d# ** ./net/http ./net/http/Mod1.d ./net/http/Mod2.d ./main.d ** I put the _ here to make it seperate from the net/http directory. Probably, a better solution exists, this was hacked together quickly :) In http_.d have: module net.http_; // again, a better solution surely exists public import net.http.Mod1; public import net.http.Mod2; Then in your main have import net.http_; You can then use whatever's in Mod1 and Mod2 modules. In your case, Mod1/Mod2 will be like HTTPConnectionRequest/HTTPConnectionResponse and will only contain a single class. This works for me. You can also go a little further and have renamed imports. Something like: public import Renamed = net.http.Mod2; Then in main.d call it with: Renamed.Mod2 mod2 = new renamed.Mod2; Feels just like Java :) Ah, I just re-read your OP. Your already at this point :)
Re: Map Lambda with Side-Effects
Unusable theoretical crap is better than the current trap :-)
We hare pure in D, but still we have not grown up to actually
use it in Phobos, for higher order functions, or parallelism.
I don't think that Nordlöw presented a serious trap. This might
lead to bugs, yes, like anything else, for example: void
foo(int[] arr) { ... arr ~= ... }
Same error, if you expect arr to be changed outside the function.
In the case of Nordlöw: If you add a warning* it will issue many
warnings for a huge amount of perfectly fine code making the
warning useless. Forbidding it, would be even worse (since the
code wouldn't work, a more verbose alternative needs to be used
etc ..). For what? To prevent a possible bug that is easily found
and fixed? Wrong trade-off if you ask me.
* When should the warning actually be issued? Whenever a closure
is passed to map? Whenever a closure passed to map closes over
something where hasAliasing!T is true?
Unicode exception raise when replacing underscore with space
I get core.exception.UnicodeException@src/rt/util/utf.d(290): in a call to std.string.tr(x, `_`, ` `) for a badly encode string x. Is it really needed to do auto-decoding here? Isn't the encoding of underscore and space uniquely one by byte in UTF-8? What do I need to do/add to avoid auto-decoding here?
Endless static this call when used a thread in it
I have written the following code:
test.d
==
import core.thread;
import std.stdio;
void threadFunc(){
writeln(Thread func);
}
public static this(){
auto t = new Thread( threadFunc );
t.start();
writeln(Static init);
}
void main(){
writeln(End of main);
}
run
==
rdmd test.d
result
==
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Static init
Thread func
Sta...
Is this normal, what's happening?
Re: Accessing class with module name as Java's
V Tue, 13 Jan 2015 10:58:27 +
tcak via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
napsáno:
Ah, I just re-read your OP. Your already at this point :)
Since everybody has understood the problem, and nobody could have
come up with a solution yet, my idea is that:
HttpSocketConnectionRequest.d
=
module net.http.HttpSocketConnectionRequest;
module class HttpSocketConnectionRequest{}
If compiler allowed module keyword to be used as an attribute
for ONLY ONE class or struct definition in the module as above,
module's name could be used as you were to be pointing to class
directly.
This would let us (and Phobos developers) to be able to separate
code files into multiple files much easily, and solve my problem
as well :).
There is a way around:
-- main.d --
import std.stdio;
import net.http;
void main(string[] arg)
{
auto p = new net.http.HttpSocketConnectionRequest();
}
-- net/http/package.d --
module net.http;
private import net.http.http_socket_connection_request;
-- net/http/http_socket_connection_request.d --
module net.http.http_socket_connection_request;
class HttpSocketConnectionRequest {
}
or
-- main.d --
import std.stdio;
static import net.http;
void main(string[] arg)
{
auto p = new net.http.HttpSocketConnectionRequest();
}
-- net/http/package.d --
module net.http;
import net.http.http_socket_connection_request;
-- net/http/http_socket_connection_request.d --
module net.http.http_socket_connection_request;
class HttpSocketConnectionRequest {
}
Re: Map Lambda with Side-Effects
ketmar: in no way. this just turns Phobos into the same unusable crap, removing the whole sense of having good standard library. If your language has purity, and it doesn't use it where it matters, you have removed its sense of having purity. So if you are right then purity in D is useless and Rust has chosen better than D on this. Bye, bearophile
Re: Unicode exception raise when replacing underscore with space
V Tue, 13 Jan 2015 12:32:15 + Nordlöw via Digitalmars-d-learn digitalmars-d-learn@puremagic.com napsáno: I get core.exception.UnicodeException@src/rt/util/utf.d(290): in a call to std.string.tr(x, `_`, ` `) for a badly encode string x. Is it really needed to do auto-decoding here? Isn't the encoding of underscore and space uniquely one by byte in UTF-8? What do I need to do/add to avoid auto-decoding here? std.array.replace(x, `_`, ` `);
Read from stdin without blocking
I want to read all input from stdin without blocking. That means I simply want to read the remaining input from stdin. All ways I tried so far always end up in me waiting for the user to enter additional input, which is not what I want. I tried around a lot with D's files / streams but couldn't find any way to do that. Any help is appreciated. Kind Regards Benjamin Thaut
Re: Cast a struct to void*
On Friday, 9 January 2015 at 19:03:04 UTC, Steven Schveighoffer
wrote:
On 1/9/15 1:50 PM, John Colvin wrote:
On Friday, 9 January 2015 at 18:35:56 UTC, anonymous wrote:
On Friday, 9 January 2015 at 18:25:42 UTC, John Colvin wrote:
struct S
{
void* p;
}
void main()
{
S s;
auto a = cast(void*)s; //Error: e2ir: cannot cast s of
type S to
type void*
This is actually a compiler bug!
So it is! The same happens with e.g. casting void* to string.
Annoyingly it passes __traits(compiles, ...)
Re: How to do equivalent of npm install --save with dub?
On 1/13/2015 10:01 AM, Andrew Grace wrote: I am trying to play with D, but I'm getting stuck with the DUB package manager. If use DUB to download a package to my project, how do I get DUB to add what I downloaded to the dub.json file? I have tried DUB --fetch --cache=local http-parser (for example). It downloads the package, but then nothing is added to the list of dependencies. I'd appreciate any help. As Rikki said, you don't need to download anything. You've got it rather backwards. *You* add the dependency to the dub.json and then *DUB* will pull it down and compile it automatically when you execute 'dub' or 'dub build' in the same directory as the configuration file. See the dub.json at [1] as an example. It's a simple little TicTacToe game that has a dependency on DerelictSDL2, which, if you look at [2], you'll find has a dependency on DerelictUtil. If you clone the source, cd into the top-level directory and execute 'dub', then DUB will pull down both DerelictUtil and DerelictSDL2, compile them into libraries, compile the game code, then link it with the libraries and run the executable. [1] https://github.com/aldacron/t3/blob/master/dub.json [2] https://github.com/DerelictOrg/DerelictSDL2/blob/master/package.json
A naive attempt at a refcounted class proxy
This discussion:
http://forum.dlang.org/thread/bqtcdpsopxmnfbjyr...@forum.dlang.org
-- led me wondering if it would be possible to create some
crippled version of a class proxy that is based on RefCounted and
came up with something like this:
struct Box(T) if (is(T == class)) {
@disable this();
this(Args...)(Args args) {
_payload._refCounted.initialize(new T(args));
}
private {
struct _Box(T) {
private T _instance;
~this() {
destroy(_instance);
}
}
RefCounted!(_Box!T) _payload;
}
~this() {
}
auto opDispatch(string name, Args...)(Args args) {
return mixin(_payload._instance.%s(args).format(name));
}
}
which lets you create Box!SomeClass(args) and it will be
refcounted unless you escape references and do other weird stuff.
It actually sort of seems to work at first glance, at least it
seems like it does... But with my D experience being fairly
limited I wonder what the potential pitfalls would be?
Full source code with example and stdout:
https://gist.github.com/aldanor/d5fb5e45ddf3dd2cb642
Re: D Beginner Trying Manual Memory Management
On Tuesday, 13 January 2015 at 08:33:57 UTC, ketmar via Digitalmars-d-learn wrote: On Mon, 12 Jan 2015 22:07:13 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: I see, thanks! :) I've started liking structs more and more recently as well and been pondering on how to convert a class-based code that looks like this (only the base class has any data): it's hard to tell by brief description. but having multiple inheritance immediately rings an alarm ring for me. something is very-very-very wrong if you need to have a winged whale. ;-) A real-world example: http://www.hdfgroup.org/HDF5/doc/cpplus_RM/hierarchy.html H5::File is both an H5::Location and H5::CommonFG (but not an H5::Object) H5::Group is both an H5::Object (subclass of H5::Location) and H5::CommonFG H5::Dataset is an H5::Object
Re: D Beginner Trying Manual Memory Management
On Tue, 13 Jan 2015 16:08:15 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: On Tuesday, 13 January 2015 at 08:33:57 UTC, ketmar via Digitalmars-d-learn wrote: On Mon, 12 Jan 2015 22:07:13 + aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: I see, thanks! :) I've started liking structs more and more recently as well and been pondering on how to convert a class-based code that looks like this (only the base class has any data): it's hard to tell by brief description. but having multiple inheritance immediately rings an alarm ring for me. something is very-very-very wrong if you need to have a winged whale. ;-) A real-world example: http://www.hdfgroup.org/HDF5/doc/cpplus_RM/hierarchy.html H5::File is both an H5::Location and H5::CommonFG (but not an H5::Object) H5::Group is both an H5::Object (subclass of H5::Location) and H5::CommonFG H5::Dataset is an H5::Object i see something named CommonFG here, which seems to good thing to move out of hierarchy altogether. bwah, i don't even sure that given hierarchy is good for D. C++ has no UFCS, and it's incredibly hard to check if some entity has some methods/properties in C++, so they have no other choice than to work around that limitations. it may be worthful to redesign the whole thing for D, exploiting D shiny UFCS and metaprogramming features. and, maybe, moving some things to interfaces too. signature.asc Description: PGP signature
Re: A naive attempt at a refcounted class proxy
On Tue, 13 Jan 2015 16:17:51 +
aldanor via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
wrote:
This discussion:
http://forum.dlang.org/thread/bqtcdpsopxmnfbjyr...@forum.dlang.org
-- led me wondering if it would be possible to create some
crippled version of a class proxy that is based on RefCounted and
came up with something like this:
struct Box(T) if (is(T == class)) {
@disable this();
this(Args...)(Args args) {
_payload._refCounted.initialize(new T(args));
}
private {
struct _Box(T) {
private T _instance;
~this() {
destroy(_instance);
}
}
RefCounted!(_Box!T) _payload;
}
~this() {
}
auto opDispatch(string name, Args...)(Args args) {
return mixin(_payload._instance.%s(args).format(name));
}
}
which lets you create Box!SomeClass(args) and it will be
refcounted unless you escape references and do other weird stuff.
It actually sort of seems to work at first glance, at least it
seems like it does... But with my D experience being fairly
limited I wonder what the potential pitfalls would be?
Full source code with example and stdout:
https://gist.github.com/aldanor/d5fb5e45ddf3dd2cb642
it's not that hard to make a boxed class. what is really hard is to
make functions that expects the class itself to accept it's boxed
variant too and behave correctly with it.
either you have to unbox it (and then hope that it will not leak), or
write two set of functions, for real class and for boxed one. and
then you may want to inherit from your class and pass that inherited
class to one of the functions... and now you have three sets. and so
on...
as structs can't be inherited, there is no such problem for structs.
signature.asc
Description: PGP signature
Re: reinterpret array
On Tuesday, 13 January 2015 at 20:11:45 UTC, anonymous wrote: On Tuesday, 13 January 2015 at 20:00:57 UTC, Dominikus Dittes Scherkl wrote: So if I have a function that allowes to do this: uint a; a.bit[16] = true; writeln(a); // 65536 Is it also already available? a |= 1 16; Of course you can calculate it, but the syntax looks quite different if you want to do a.bit[22] = false: a = ~(116); Or if you want to test a bit: if(a.bit[16]) instead of if(a (116)) much more convenient for arrays: ulong[100] a; a.bit[3000] = true; doing this directly with shifts is lousy (and error prone) But ok. I see, it's not really awesome :-/
Re: reinterpret array
On Tue, 13 Jan 2015 20:52:13 +
Dominikus Dittes Scherkl via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com wrote:
On Tuesday, 13 January 2015 at 20:11:45 UTC, anonymous wrote:
On Tuesday, 13 January 2015 at 20:00:57 UTC, Dominikus Dittes
Scherkl wrote:
So if I have a function that allowes to do this:
uint a;
a.bit[16] = true;
writeln(a); // 65536
Is it also already available?
a |= 1 16;
Of course you can calculate it, but the
syntax looks quite different if you want to do
a.bit[22] = false:
a = ~(116);
Or if you want to test a bit:
if(a.bit[16])
instead of
if(a (116))
much more convenient for arrays:
ulong[100] a;
a.bit[3000] = true;
doing this directly with shifts is lousy (and error prone)
But ok. I see, it's not really awesome :-/
it's not better than using something like this:
a.bitSet(22);
a.bitReset(30);
if (a.bit(16)) { ... }
you can easily do this with UFCS. you can even write some templates to
convert it to bit operations in compile time.
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Description: PGP signature
Re: reinterpret array
On Tue, 13 Jan 2015 20:00:56 + Dominikus Dittes Scherkl via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: p.s. i don't intend to stop you from doing what you want to do, in no way. i was just trying to show you some things that you can accidentally missed. sorry if it looks like stop it, we already have one and nobody should need more of that! signature.asc Description: PGP signature
Re: Unicode exception raise when replacing underscore with space
On Tuesday, 13 January 2015 at 20:30:16 UTC, Nordlöw wrote:
On Tuesday, 13 January 2015 at 13:01:56 UTC, Daniel Kozák via
Digitalmars-d-learn wrote:
What do I need to do/add to avoid auto-decoding here?
std.array.replace(x, `_`, ` `);
Thanks! What about adding See alsos in the docs that relate
these two with respect to auto-decoding?
I am not sure, it doesn`t exactly do the same. And to be fair
std.array.replace use internaly std.algorithm.find which use in
some scenario auto-decoding. So to be sure no autodecoding
occured you must used something like that:
string x = some_text;
auto res = std.array.replace(cast(byte[])x, [byte('_')],
[byte(' ')]);
writeln(cast(string)res);
Re: Unicode exception raise when replacing underscore with space
On Tuesday, 13 January 2015 at 13:01:56 UTC, Daniel Kozák via Digitalmars-d-learn wrote: What do I need to do/add to avoid auto-decoding here? std.array.replace(x, `_`, ` `); Thanks! What about adding See alsos in the docs that relate these two with respect to auto-decoding?
Re: Map Lambda with Side-Effects
On Tuesday, 13 January 2015 at 07:35:53 UTC, Nordlöw wrote:
Somewhat related to
https://github.com/D-Programming-Language/phobos/pull/2024
I wonder about the soundness of `map` in
```D
import std.algorithm, std.range, std.stdio;
void main(string[] args)
{
long[] arr;
const n = 3;
iota(n).map!(a = arr ~= a);
writeln(arr);
writeln(iota(n).map!(a = arr ~= a));
writeln(arr);
}
```
that prints
```D
[]
[[0], [0, 1], [0, 1, 2]]
[0, 1, 2]
```
Shouldn't a warning at least be issued for return-ignoring calls
to map with mutating lambdas? Has there been any discussions on
making map require pure functions now that we have each? I guess
a new function, say `mapPure`, may be neccessary as adding such
a
restriction to the lambda will break too much code right?
To clarify:
I f() is stronly pure function then DMD since 2.066 will warn
about
f();
, that is, upon return-discarding calls to strongly pure function.
I believe
iota(n).map!(a = arr ~= a);
is a very similar mistake done and if possible should be warned
about.
Is it possible to
- detect that a lambda is has-side-effects and that
- the map hasn't been used?
If this can't (yet) be detected in compiled-time what about
issuing an exception in the destructor of Map to detect this?
Destroy!
Re: reinterpret array
anonymous: a |= 1 16; In D there's also the 2 ^^ x syntax available. Bye, bearophile
Re: reinterpret array
On Tuesday, 13 January 2015 at 20:52:15 UTC, Dominikus Dittes Scherkl wrote: Of course you can calculate it, but the syntax looks quite different if you want to do a.bit[22] = false: a = ~(116); Or if you want to test a bit: if(a.bit[16]) instead of if(a (116)) much more convenient for arrays: ulong[100] a; a.bit[3000] = true; doing this directly with shifts is lousy (and error prone) But ok. I see, it's not really awesome :-/ I didn't mean to put a stop to your idea just because we have bitwise operators. You're totally right: They're somewhat cumbersome and easy to get wrong. We also have std.bitmanip.BitArray which is what you're after, I think: import std.bitmanip: BitArray; BitArray ba; ba.length = 3001; ba[3000] = true;
Re: reinterpret array
On 01/13/15 21:52, Dominikus Dittes Scherkl via Digitalmars-d-learn wrote:
On Tuesday, 13 January 2015 at 20:11:45 UTC, anonymous wrote:
On Tuesday, 13 January 2015 at 20:00:57 UTC, Dominikus Dittes Scherkl wrote:
So if I have a function that allowes to do this:
uint a;
a.bit[16] = true;
writeln(a); // 65536
Is it also already available?
a |= 1 16;
Of course you can calculate it, but the
syntax looks quite different if you want to do
a.bit[22] = false:
a = ~(116);
Or if you want to test a bit:
if(a.bit[16])
instead of
if(a (116))
much more convenient for arrays:
ulong[100] a;
a.bit[3000] = true;
doing this directly with shifts is lousy (and error prone)
But ok. I see, it's not really awesome :-/
It's neat, but the real problems with it are:
1) obfuscation - it hides those trivial bit ops behind layers of
functions and operator overloads, which everyone reading the
code must then figure out;
2) safety - `a.bit` could potentially outlive `a`; D does not
handle object lifetimes, so there's no 100% safe way to prevent
such bugs.
Hence you probably don't actually want to use this.
struct Bits(E, size_t UB=1) {
E* e;
bool opIndexAssign(bool v, size_t idx) {
auto o = idx/(E.sizeof*8);
idx %= E.sizeof*8;
if (o=UB)
assert (0);
if (v)
e[o] |= 1Lidx;
else
e[o] = ~(1Lidx);
return v;
}
bool opIndex(size_t idx) {
auto o = idx/(E.sizeof*8);
idx %= E.sizeof*8;
if (o=UB)
assert (0);
return !!(e[o] 1Lidx);
}
}
auto bit(E)(ref E e) @property {
static if (is(E:A[L], A, size_t L))
return Bits!(typeof(e[0]), L)(e.ptr);
else
return Bits!E(e);
}
artur
