Re: Shortest way to allocate an array and initialize it with a specific value.
On Thursday, 11 June 2015 at 07:57:47 UTC, Per Nordlöw wrote:
On Wednesday, 10 June 2015 at 22:03:52 UTC, Ali Çehreli wrote:
Another option:
void main()
{
auto a2 = new ubyte[5];
But this causes an extra zero-initialization of a2.
a2[] = 0xAA;// -- Assign to all elements
Is
auto a2 = value.repeat(size).array;
better in this regard?
Yes, it uses `uninitializedArray()` if the length is known (which
it is for `repeat()`):
https://github.com/D-Programming-Language/phobos/blob/master/std/array.d#L111
Re: Encapsulate return value in scoped
On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10);
Re: What is D's minimum requirements on Mac?
Whee, $99/year.
Encapsulate return value in scoped
Is there a way to encapsulate return value into scoped?
Say I have a function that returns a new object:
X new_x(T t...) {
//Super complex input processing
return new X(something);
}
And I want to encapsulate the result using scoped, is that
possible? Can I just do:
return scoped!X(something).
?
If I understand correctly, the data will be blitted, but the
destructor will be called, so the returned object will be in
invalid state.
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 08:48:22 UTC, Yuxuan Shui wrote:
Is there a way to encapsulate return value into scoped?
Say I have a function that returns a new object:
X new_x(T t...) {
//Super complex input processing
return new X(something);
}
And I want to encapsulate the result using scoped, is that
possible? Can I just do:
return scoped!X(something).
?
If I understand correctly, the data will be blitted, but the
destructor will be called, so the returned object will be in
invalid state.
It's even weirder than I thought, this:
import std.stdio,
std.typecons;
class A {
int b;
~this() {
writeln(Des);
}
this(int x) {
b=x;
writeln(Cons);
}
}
auto x() {
A x = scoped!A(10);
writeln(x.b);
writeln(Return x);
return x;
}
void main() {
auto tx = x();
writeln(Return main);
}
Produce output:
Cons
Des
0
Return x
Return main
Which I totally don't understand.
Re: Shortest way to allocate an array and initialize it with a specific value.
On Thursday, 11 June 2015 at 08:33:46 UTC, Daniel Kozák wrote:
On Wed, 10 Jun 2015 20:22:17 +
Adel Mamin via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
Now, let's say, I want to allocate an array of a size, derived
at run time, and initialize it to some non-zero value at the
same time. What would be the shortest way of doing it?
import std.stdio;
struct Ubyte(ubyte defval) {
ubyte v = defval;
alias v this;
}
void main() {
auto a2 = new Ubyte!(0xAA)[5];
writeln(a2);
}
I like this one :-)
Re: What is D's minimum requirements on Mac?
On Wednesday, 10 June 2015 at 18:55:27 UTC, Adam D. Ruppe wrote: I'm still tempted to grab a used Mac so I can port my display stuff to Cocoa and test it, but Macs are outrageously expensive and I hate them, so want to spend as little as possible. What does dmd minimally require on a mac? If I got like a 10.5 would that work? i'm considering something like http://www.amazon.com/Apple-MB138LL-Intel-Drive-Combo/dp/B0006HU49Y/ref=sr_1_5?ie=UTF8qid=1433962021sr=8-5keywords=used+mac+mini You can try to register as a developer: https://developer.apple.com/programs/ and get beta versions of OSX and install them on virtual box. Not sure how much it costs.
Re: Shortest way to allocate an array and initialize it with a specific value.
On Thu, 11 Jun 2015 11:43:25 +
via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote:
On Thursday, 11 June 2015 at 08:33:46 UTC, Daniel Kozák wrote:
On Wed, 10 Jun 2015 20:22:17 +
Adel Mamin via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
Now, let's say, I want to allocate an array of a size, derived
at run time, and initialize it to some non-zero value at the
same time. What would be the shortest way of doing it?
import std.stdio;
struct Ubyte(ubyte defval) {
ubyte v = defval;
alias v this;
}
void main() {
auto a2 = new Ubyte!(0xAA)[5];
writeln(a2);
}
I like this one :-)
small enhancment:
struct Ubyte(ubyte defval = 0)
Re: Python's features, which requires D
On Saturday, 23 May 2015 at 10:58:33 UTC, Kagamin wrote:
On Saturday, 23 May 2015 at 02:36:14 UTC, Dennis Ritchie wrote:
For example, the code in Python looks quite natural:
a = [[int(j) for j in input().split()] for i in range(n)]
About D-code, I can not say:
auto a = stdin
.byLine
.map!(l = l.splitter.map!(to!int).array)
.take(n);
Well, list comprehension is built into language in python (and
not in D), such level of support is definitely more streamlined.
Yes, but D is also possible to create a strong inclusion of list
comprehensions. Here's the proof:
https://github.com/pplantinga/delight
Probably the coolest feature in Delight is list comprehensions.
Delight uses functions in std.algorithm to generate an iterable
range. The syntax is similar to Python's. See the last two
lines of the code above for an example.
print { i * 2 for i in 0 .. 5 where i ^ 2 less than 5 }
# prints [0, 2, 4]
Re: Shortest way to allocate an array and initialize it with a specific value.
On 6/11/15 7:51 AM, Daniel Kozák via Digitalmars-d-learn wrote:
On Thu, 11 Jun 2015 11:43:25 +
via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote:
On Thursday, 11 June 2015 at 08:33:46 UTC, Daniel Kozák wrote:
On Wed, 10 Jun 2015 20:22:17 +
Adel Mamin via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
Now, let's say, I want to allocate an array of a size, derived
at run time, and initialize it to some non-zero value at the
same time. What would be the shortest way of doing it?
import std.stdio;
struct Ubyte(ubyte defval) {
ubyte v = defval;
alias v this;
}
void main() {
auto a2 = new Ubyte!(0xAA)[5];
writeln(a2);
}
I like this one :-)
small enhancment:
struct Ubyte(ubyte defval = 0)
import std.typecons;
alias Ubyte(ubyte defval = 0) = Typedef!(ubyte, defval);
I personally like the range solution the best, it has the most flexibility.
-Steve
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code?
Re: Encapsulate return value in scoped
On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 17:34:56 UTC, Steven Schveighoffer wrote: On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve Thanks! I just found that out myself. Learned 'alias this' in the process.
Re: Encapsulate return value in scoped
On 06/11/2015 11:43 AM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 17:34:56 UTC, Steven Schveighoffer wrote: On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve Thanks! I just found that out myself. Learned 'alias this' in the process. Shameless plug: :) http://ddili.org/ders/d.en/destroy.html#ix_destroy.scoped This issue is explained at the end of that section. Ali
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 19:23:49 UTC, Ali Çehreli wrote: On 06/11/2015 11:43 AM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 17:34:56 UTC, Steven Schveighoffer wrote: On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve Thanks! I just found that out myself. Learned 'alias this' in the process. Shameless plug: :) http://ddili.org/ders/d.en/destroy.html#ix_destroy.scoped This issue is explained at the end of that section. Ali Can you explain more about why the destructor is not called when returning a struct? Can't seem to find it in the document.
Reading array of integers readln performance issues
Hi; To learn D better and challanging myself I am tring code computation's with D. There is a question which is about reading a line of integer which consist of 20 elements. My solution fails because Time limit exceeded, I thought it is because of my algorithm first. I realize time limit is exceeded even before my algorithm starts while reading line of integers. I understand this by giving a wrong answer to question after readln statement. I did that to get a wrong answer error but my code still get a Time limit exceed error because readln takes very long time. Can I achieve something faster than code below? auto peopleMoney = stdin.readln().split().map!(a = to!int(a)).array(); if (peopleMoney.length == 20) writeln(:(); Regards Erdem Ps: I do not want to bore you with long code, but I am sending link to whole program anyway if anyone need. http://codeforces.com/contest/549/submission/11537206
.sizeof dynamically allocated array
import std.stdio;
void main()
{
ubyte[] a1 = new ubyte[65];
ubyte[65] a2;
writeln(a1.sizeof = , a1.sizeof); // prints 16
writeln(a2.sizeof = , a2.sizeof); // prints 65
}
Why a1.sizeof is 16?
Re: .sizeof dynamically allocated array
On Thursday, 11 June 2015 at 20:09:38 UTC, Adel Mamin wrote: Why a1.sizeof is 16? sizeof is tied to *type*, not a variable. (I kinda wish a1.sizeof was prohibited, forcing you to say typeof(a1).sizeof so it is clear but whatever). A dynamic array's size is the length variable plus the pointer variable. A static array's size is the content itself. If you want the size of the content in bytes, best way is to do (cast(ubyte[]) a1[]).length or somethign like that - use the length property instead of sizeof.
Re: .sizeof dynamically allocated array
On Thursday, 11 June 2015 at 20:09:38 UTC, Adel Mamin wrote:
import std.stdio;
void main()
{
ubyte[] a1 = new ubyte[65];
ubyte[65] a2;
writeln(a1.sizeof = , a1.sizeof); // prints 16
writeln(a2.sizeof = , a2.sizeof); // prints 65
}
Why a1.sizeof is 16?
ubyte[] is a slice, which is actually a struct. It's more or less
the same as:
struct Slice(T)
{
T* ptr;
size_t length;
}
So sizeof returns the size of the struct, not the size of the
data that its ptr member points to.
ubyte[65] is a static array, which is just a big block of data on
the stack. That's why it returns the expected value for sizeof.
To create a slice of a static array, use the slice operator:
writeln(sizeof(a2[])); //Prints 16
Re: Shortest way to allocate an array and initialize it with a specific value.
On Thursday, 11 June 2015 at 07:57:47 UTC, Per Nordlöw wrote:
On Wednesday, 10 June 2015 at 22:03:52 UTC, Ali Çehreli wrote:
Another option:
void main()
{
auto a2 = new ubyte[5];
But this causes an extra zero-initialization of a2.
just an fyi, gdc optimizes this away(looks like it overwrites the
typeinfo,) ldc does not.
Re: Reading array of integers readln performance issues
On Thursday, 11 June 2015 at 19:56:00 UTC, kerdemdemir wrote: Can I achieve something faster than code below? auto peopleMoney = stdin.readln().split().map!(a = to!int(a)).array(); if (peopleMoney.length == 20) writeln(:(); `std.array.split` is eager. It may be faster if you use the lazy `std.algorithm.splitter`: auto peopleMoney = stdin.readln().splitter().map!(to!int).array(); [...] Ps: I do not want to bore you with long code, but I am sending link to whole program anyway if anyone need. http://codeforces.com/contest/549/submission/11537206 Seeing that you get the number of elements beforehand, you can preallocate the array, avoiding relocations of the data as elements are appended: peopleMoney = new int[peopleCount]; copy(stdin.readln().splitter().map!(to!int), peopleMoney); But these are tweaks. They may improve performance a little, but it won't be drastic. And anyway, I find it hard to believe that the original version takes more than a second to parse the input. Maybe try returning from the function in addition to printing :(. Otherwise the program goes on, and the site may not show the output if the program as a whole took too long.
Re: Reading array of integers readln performance issues
On Thursday, 11 June 2015 at 19:56:00 UTC, kerdemdemir wrote: Hi; To learn D better and challanging myself I am tring code computation's with D. There is a question which is about reading a line of integer which consist of 20 elements. My solution fails because Time limit exceeded, I thought it is because of my algorithm first. I realize time limit is exceeded even before my algorithm starts while reading line of integers. I understand this by giving a wrong answer to question after readln statement. I did that to get a wrong answer error but my code still get a Time limit exceed error because readln takes very long time. Can I achieve something faster than code below? auto peopleMoney = stdin.readln().split().map!(a = to!int(a)).array(); if (peopleMoney.length == 20) writeln(:(); Regards Erdem Ps: I do not want to bore you with long code, but I am sending link to whole program anyway if anyone need. http://codeforces.com/contest/549/submission/11537206 Your algorithm works for about quadratic time. For N = 20 your algorithm will work terribly long. The function `readln()` nothing to do with: http://codeforces.com/contest/549/submission/11476513 A faster way of `scanf`, but it will not help you, because your algorithm is slow.
Re: Json
On Thursday, 11 June 2015 at 23:58:33 UTC, Cassio Butrico wrote:
What does the .json file and how to use it?
In D a file with the extension *.json is used to describe packets
that are included in your project, the dependency manager DUB.
For example, you can install Eclipse with DDT and create a
project with DUB. The file dub.json write the following:
-
{
name : myDupApp,
description : Carbon - Test.,
dependencies : {
carbon: ~1.4.1
}
}
-
Save the file (Ctrl + S). Then in your project with DUB
downloaded package `carbon`:
http://code.dlang.org/packages/carbon
After that you can safely use the package `carbon`:
-
import std.stdio, carbon.linear;;
void main() {
auto m = matrix!(2, 3, (i, j) = i * 3 + j);
writeln(m); // [[0, 1, 2], [3, 4, 5]]
}
Re: Json
On Friday, 12 June 2015 at 00:35:35 UTC, Cassio Butrico wrote: Thank you for answering me so fast , where do I get the DUB for windows ? http://code.dlang.org/download
Json
What does the .json file and how to use it?
Re: Json
Thank you for answering me so fast , where do I get the DUB for windows ?
Re: Json
On 06/11/2015 04:58 PM, Cassio Butrico wrote: What does the .json file and how to use it? There is also the .json file that is produced by dmd's -X command line switch: dmd -X foo.d That outputs the members of the source code to foo.json in a way that may be useful for a tool. Ali
Re: Json
On Friday, 12 June 2015 at 00:56:45 UTC, Ali Çehreli wrote: On 06/11/2015 04:58 PM, Cassio Butrico wrote: What does the .json file and how to use it? There is also the .json file that is produced by dmd's -X command line switch: dmd -X foo.d That outputs the members of the source code to foo.json in a way that may be useful for a tool. Ali Thanks Ali , I did not know that. :) I really like your tutorial is great for goods .
Re: Shortest way to allocate an array and initialize it with a specific value.
On Wednesday, 10 June 2015 at 22:03:52 UTC, Ali Çehreli wrote:
Another option:
void main()
{
auto a2 = new ubyte[5];
But this causes an extra zero-initialization of a2.
a2[] = 0xAA;// -- Assign to all elements
Is
auto a2 = value.repeat(size).array;
better in this regard?
Re: Shortest way to allocate an array and initialize it with a specific value.
On Wed, 10 Jun 2015 20:22:17 +
Adel Mamin via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
wrote:
ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
Now, let's say, I want to allocate an array of a size, derived at
run time, and initialize it to some non-zero value at the same
time. What would be the shortest way of doing it?
import std.stdio;
struct Ubyte(ubyte defval) {
ubyte v = defval;
alias v this;
}
void main() {
auto a2 = new Ubyte!(0xAA)[5];
writeln(a2);
}
