Is a type not a symbol?

[Shriramana Sharma via Digitalmars-d-learn]

http://dlang.org/spec/template.html#TemplateTupleParameter

says that an AliasSeq (wording needs to be updated) "is a sequence of any 
mix of types, expressions or symbols."

Is a type not a symbol? I mean, alias can refer to both, no?

-- 
Shriramana Sharma, Penguin #395953

: in template specialization vs constraint

[Shriramana Sharma via Digitalmars-d-learn]

import std.stdio;
void func(T)(T v) { writeln(1); }
void func(T: int)(T v) { writeln(2); }
void func(T)(T v) if (is(T: int)) { writeln(3); }
void main()
{
func(100);
ubyte s = 200;
func(s);
}

The above code prints 2 twice. A fwe questions:

1) At func(100) why isn't the compiler complaining that it is able to match 
two templates i.e. the ones printing 2 and 3? Is it that since the second 
one is specialized but the third one apparently isn't, the compiler just 
ignores the third one?

2) How come func(s) doesn't invoke the template that prints 3? `T: int` in 
the context of specialization means an exact match but in the context of 
constraints it means implicitly convertible, no? The specialization section 
under http://dlang.org/spec/template.html is not very clear about this IMHO.

-- 
Shriramana Sharma, Penguin #395953

Re: Let dmd or ldc be easy to setup on Ubuntu

[FrankLike via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 14:37:21 UTC, Rikki Cattermole 
wrote:

I'm confused.
The commands listed e.g.

$ sudo wget 
http://netcologne.dl.sourceforge.net/project/d-apt/files/d-apt.list -O /etc/apt/sources.list.d/d-apt.list
$ sudo apt-get update && sudo apt-get -y 
--allow-unauthenticated install --reinstall d-apt-keyring && 
sudo apt-get update


Should work.
If it does not, please post output.


Sorry, it works,but can't get any useful info.

Re: Let dmd or ldc be easy to setup on Ubuntu

[FrankLike via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 15:08:20 UTC, FrankLike wrote:
On Tuesday, 22 December 2015 at 14:37:21 UTC, Rikki Cattermole 
wrote:

I'm confused.
The commands listed e.g.

$ sudo wget 
http://netcologne.dl.sourceforge.net/project/d-apt/files/d-apt.list -O /etc/apt/sources.list.d/d-apt.list
$ sudo apt-get update && sudo apt-get -y 
--allow-unauthenticated install --reinstall d-apt-keyring && 
sudo apt-get update


Should work.
If it does not, please post output.


Sorry, it works,but can't get any useful info.

sudo apt-get install dmd ← it's error.
Now I setup by double click the 'dmd_2.069.2-0-amd64.deb' 
file,and setup it.

then sudo apt-get install dub
it's ok.

Re: : in template specialization vs constraint

[Adam D. Ruppe via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 15:29:16 UTC, Shriramana Sharma 
wrote:
1) At func(100) why isn't the compiler complaining that it is 
able to match two templates i.e. the ones printing 2 and 3?


Because the specialized one just wins the context. It only 
complains when there's two equal ones.


Constraints serve only to add or remove the template from the 
consideration list. If the constraint fails, the compiler 
considers that template to not even exist. If it passes, it adds 
the template to the overload list and then proceeds like it 
normally would without looking at the constraint again.


Since your constraint passed, #3 is added to the list along side 
#1 and #2. Then, since #2 is specialized, it gets picked instead 
of the others.


2) How come func(s) doesn't invoke the template that prints 3? 
`T: int` in the context of specialization means an exact match 
but in the context of constraints it means implicitly 
convertible, no? The specialization section under 
http://dlang.org/spec/template.html is not very clear about 
this IMHO.


In specialization, it will implicitly convert, it will just 
select the best match available.


Make #1:

void func(T : ubyte)(T v) { writeln(1); }

It will then use that for for the second line because it is a 
*better* match than :int, but :int still is a match so it works 
as a fallback.

Re: Is a type not a symbol?

[Adam D. Ruppe via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 15:22:49 UTC, Shriramana Sharma 
wrote:

Is a type not a symbol? I mean, alias can refer to both, no?


Keywords aren't symbols so `int` is a type, but not a symbol and 
thus qualifies as `T` but not as `alias T`.

Re: Let dmd or ldc be easy to setup on Ubuntu

[Jordi Sayol via Digitalmars-d-learn]

El 22/12/15 a les 18:28, Jordi Sayol via Digitalmars-d-learn ha escrit:
> "d-lang" splits it in few deb packages:

s/d-lang/d-apt/

Re: Most performant way of converting int to string

[Daniel Kozák via Digitalmars-d-learn]

V Tue, 22 Dec 2015 18:39:16 +
Ivan Kazmenko via Digitalmars-d-learn
 napsáno:

> On Tuesday, 22 December 2015 at 18:11:24 UTC, rumbu wrote:
> > On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
> > wrote:  
> >> Sorry if this is a silly question but is the to! method from 
> >> the conv library the most efficient way of converting an 
> >> integer value to a string?
> >>
> >> e.g.
> >> string s = to!string(100);
> >>
> >> I'm seeing a pretty dramatic slow down in my code when I use a 
> >> conversion like this (when looped over 10 million iterations 
> >> for benchmarking).
> >>
> >> Cheers!  
> >
> > Converting numbers to string involves the most expensive known 
> > two operations : division and modulus by 10.  
> 
> When the base is known in advance, division and modulus can be 
> substituted by a few additions, subtractions and bit shifts.  For 
> example, the Hacker's Delight book has a chapter dedicated to 
> that, as well as a freely available additional chapter 
> (www.hackersdelight.org/divcMore.pdf).
> 
> Does DMD, or Phobos function to!(string), do anything like that?  
> The number of possible bases is not large anyway.  I've heard 
> major C/C++ compilers do that, but have not looked for a proof 
> myself.

Yes, IIRC, all D compilers should be able to change modulus and
division to few additions, subtractions and bit shifts if base is known
at compile time.

And phobos use this:
https://github.com/D-Programming-Language/phobos/pull/1452

MonoTime longevity

[Tanel Tagaväli via Digitalmars-d-learn]

I discovered something potentially troublesome in druntime.
Namely, applications that use MonoTime will break if run 18 hours 
after booting, according to a short program I wrote.


Here's my code:

```
import core.time : MonoTime;
auto mt = MonoTime.currTime;
import std.stdio : writeln;
writeln(mt.ticks / mt.ticksPerSecond / 60 / 60); // prints 18 
(hours) shortly after boot

```

`mt.ticksPerSecond` is `1_000_000_000` on my system.
I really hope I'm doing something wrong.

Re: MonoTime longevity

[Tanel Tagaväli via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 20:07:58 UTC, Steven 
Schveighoffer wrote:
MonoTime uses whatever precision is given to it by the OS. So 
if on your OS, ticksPerSecond is 1e9, then your OS clock wraps 
at 18 hours as well.

Thanks, I didn't know that.

I actually just realized that my use case doesn't need to rely on 
absolute clocks, so I'm safe.

Re: Most performant way of converting int to string

[Daniel Kozák via Digitalmars-d-learn]

V Tue, 22 Dec 2015 18:11:24 +
rumbu via Digitalmars-d-learn 
napsáno:

> On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
> wrote:
> > Sorry if this is a silly question but is the to! method from 
> > the conv library the most efficient way of converting an 
> > integer value to a string?
> >
> > e.g.
> > string s = to!string(100);
> >
> > I'm seeing a pretty dramatic slow down in my code when I use a 
> > conversion like this (when looped over 10 million iterations 
> > for benchmarking).
> >
> > Cheers!  
> 
> Converting numbers to string involves the most expensive known 
> two operations : division and modulus by 10.

No, IIRC few months or maybe years I have optimize this so it does not
use division and modulus

Re: Most performant way of converting int to string

[rumbu via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
wrote:
Sorry if this is a silly question but is the to! method from 
the conv library the most efficient way of converting an 
integer value to a string?


e.g.
string s = to!string(100);

I'm seeing a pretty dramatic slow down in my code when I use a 
conversion like this (when looped over 10 million iterations 
for benchmarking).


Cheers!


Converting numbers to string involves the most expensive known 
two operations : division and modulus by 10.

Re: Most performant way of converting int to string

[Daniel Kozák via Digitalmars-d-learn]

V Tue, 22 Dec 2015 17:15:27 +
Andrew Chapman via Digitalmars-d-learn
 napsáno:

> Sorry if this is a silly question but is the to! method from the 
> conv library the most efficient way of converting an integer 
> value to a string?
> 
> e.g.
> string s = to!string(100);
> 
> I'm seeing a pretty dramatic slow down in my code when I use a 
> conversion like this (when looped over 10 million iterations for 
> benchmarking).
> 
> Cheers!
> 
> 

This is OK and expected :).

Re: Most performant way of converting int to string

[Daniel Kozák via Digitalmars-d-learn]

V Tue, 22 Dec 2015 20:52:07 +
rumbu via Digitalmars-d-learn 
napsáno:

> On Tuesday, 22 December 2015 at 19:45:46 UTC, Daniel Kozák wrote:
> > V Tue, 22 Dec 2015 18:11:24 +
> > rumbu via Digitalmars-d-learn 
> > 
> > napsáno:
> >  
> >> On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
> >> wrote:  
> >> > Sorry if this is a silly question but is the to! method from 
> >> > the conv library the most efficient way of converting an 
> >> > integer value to a string?
> >> >
> >> > e.g.
> >> > string s = to!string(100);
> >> >
> >> > I'm seeing a pretty dramatic slow down in my code when I use 
> >> > a conversion like this (when looped over 10 million 
> >> > iterations for benchmarking).
> >> >
> >> > Cheers!  
> >> 
> >> Converting numbers to string involves the most expensive known 
> >> two operations : division and modulus by 10.  
> >
> > No, IIRC few months or maybe years I have optimize this so it 
> > does not use division and modulus  
> 
> It's using division and modulus, as expected:
> 
> https://github.com/D-Programming-Language/phobos/blob/master/std/conv.d#L5529
> 
> If the compiler is smart enough, maybe it will replace this by 
> well known multiplication trick.

Yes compiler is smart enought so it will not use division and modulus
as I say before :)

Re: Most performant way of converting int to string

[Andrew Chapman via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 18:11:24 UTC, rumbu wrote:
On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
wrote:
Sorry if this is a silly question but is the to! method from 
the conv library the most efficient way of converting an 
integer value to a string?


e.g.
string s = to!string(100);

I'm seeing a pretty dramatic slow down in my code when I use a 
conversion like this (when looped over 10 million iterations 
for benchmarking).


Cheers!


Converting numbers to string involves the most expensive known 
two operations : division and modulus by 10.


Cool thanks, so essentially it's unavoidable - I have a 
background in PHP programming where we don't really get exposed 
to memory allocation, conversions etc.  Good to learn.  Cheers.

Re: MonoTime longevity

[Steven Schveighoffer via Digitalmars-d-learn]

On 12/22/15 2:48 PM, Tanel Tagaväli wrote:

I discovered something potentially troublesome in druntime.
Namely, applications that use MonoTime will break if run 18 hours after
booting, according to a short program I wrote.

Here's my code:

```
import core.time : MonoTime;
auto mt = MonoTime.currTime;
import std.stdio : writeln;
writeln(mt.ticks / mt.ticksPerSecond / 60 / 60); // prints 18 (hours)
shortly after boot
```

`mt.ticksPerSecond` is `1_000_000_000` on my system.
I really hope I'm doing something wrong.


MonoTime uses whatever precision is given to it by the OS. So if on your 
OS, ticksPerSecond is 1e9, then your OS clock wraps at 18 hours as well.


In a recent version of D, MonoTime was changed to support multiple 
clocks. Use MonoTimeImpl!SomeClockType to use a clock with a different 
number of ticks per second if one exists.


You can also use std.datetime.Clock

-Steve

Re: Most performant way of converting int to string

[rumbu via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 20:52:07 UTC, rumbu wrote:
On Tuesday, 22 December 2015 at 19:45:46 UTC, Daniel Kozák 
wrote:

V Tue, 22 Dec 2015 18:11:24 +
rumbu via Digitalmars-d-learn 


napsáno:

On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
wrote:
> Sorry if this is a silly question but is the to! method 
> from the conv library the most efficient way of converting 
> an integer value to a string?

>
> e.g.
> string s = to!string(100);
>
> I'm seeing a pretty dramatic slow down in my code when I 
> use a conversion like this (when looped over 10 million 
> iterations for benchmarking).

>
> Cheers!

Converting numbers to string involves the most expensive 
known two operations : division and modulus by 10.


No, IIRC few months or maybe years I have optimize this so it 
does not use division and modulus


It's using division and modulus, as expected:

https://github.com/D-Programming-Language/phobos/blob/master/std/conv.d#L5529

If the compiler is smart enough, maybe it will replace this by 
well known multiplication trick.


Tested it, I was right:

No optimizations: two divisions, one for the modulus and one for 
the division itself

Optimized: multiplication by 0xCCCD trick.

http://imgur.com/a/lHeHe

Re: Most performant way of converting int to string

[H. S. Teoh via Digitalmars-d-learn]

On Tue, Dec 22, 2015 at 08:54:35PM +0100, Daniel Kozák via Digitalmars-d-learn 
wrote:
> V Tue, 22 Dec 2015 09:43:00 -0800
> "H. S. Teoh via Digitalmars-d-learn"
>  napsáno:
> 
> > On Tue, Dec 22, 2015 at 05:23:11PM +, Andrew Chapman via
> > Digitalmars-d-learn wrote: [...]
> > > for({int i; i = 0;} i < num; i++) {
> > > //string s = to!string(i);
> > > Customer c = Customer(i, "Customer", "", i
> > > * 2); string result = objS.serialize(c);
> > > }
> > > 
> > > If I uncomment the "string s" line I'm seeing a 20% increase in
> > > running time, which given what's going on the rest of the code is
> > > quite surprising.  I've tried compiling with both dmd and ldc2 -
> > > it's the same under both.  
> > [...]
> > 
> > I wonder if the slowdown is caused by GC collection cycles (because
> > calling to!string will allocate, and here you're making a very large
> > number of small allocations, which is known to cause GC performance
> > issues).
> > 
> > Try inserting this before the loop:
> > 
> > import core.memory;
> > GC.disable();
> > 
> > Does this make a difference in the running time?
> > 
> > 
> > T
> > 
> This would  not help. It would probably be worse.

I was not suggesting this as a solution, it's merely a way to determine
whether the performance issue is GC-related.


T

-- 
"Hi." "'Lo."

Re: Most performant way of converting int to string

[Daniel Kozák via Digitalmars-d-learn]

V Tue, 22 Dec 2015 21:10:54 +
rumbu via Digitalmars-d-learn 
napsáno:

> On Tuesday, 22 December 2015 at 20:52:07 UTC, rumbu wrote:
> > On Tuesday, 22 December 2015 at 19:45:46 UTC, Daniel Kozák 
> > wrote:  
> >> V Tue, 22 Dec 2015 18:11:24 +
> >> rumbu via Digitalmars-d-learn 
> >> 
> >> napsáno:
> >>  
> >>> On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
> >>> wrote:  
> >>> > Sorry if this is a silly question but is the to! method 
> >>> > from the conv library the most efficient way of converting 
> >>> > an integer value to a string?
> >>> >
> >>> > e.g.
> >>> > string s = to!string(100);
> >>> >
> >>> > I'm seeing a pretty dramatic slow down in my code when I 
> >>> > use a conversion like this (when looped over 10 million 
> >>> > iterations for benchmarking).
> >>> >
> >>> > Cheers!  
> >>> 
> >>> Converting numbers to string involves the most expensive 
> >>> known two operations : division and modulus by 10.  
> >>
> >> No, IIRC few months or maybe years I have optimize this so it 
> >> does not use division and modulus  
> >
> > It's using division and modulus, as expected:
> >
> > https://github.com/D-Programming-Language/phobos/blob/master/std/conv.d#L5529
> >
> > If the compiler is smart enough, maybe it will replace this by 
> > well known multiplication trick.  
> 
> Tested it, I was right:
> 
> No optimizations: two divisions, one for the modulus and one for 
> the division itself
> Optimized: multiplication by 0xCCCD trick.
> 
> http://imgur.com/a/lHeHe
> 
> 

Yes this is expected :).

Re: How is D doing?

[Cavanni via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 03:43:24 UTC, ShinraTensei wrote:
A friend of mine told me that my post might have sounded a bit 
trollish i assure you that was not the case.


In fact it sounds very nonsense to me. You know you just came 
here asking on a "D FORUM" if the "D Programming Language" will 
die anytime soon...


So... expecting what? A fan confirming this?

Re: How is D doing?

[ShinraTensei via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 21:58:24 UTC, Cavanni wrote:
On Tuesday, 22 December 2015 at 03:43:24 UTC, ShinraTensei 
wrote:
A friend of mine told me that my post might have sounded a bit 
trollish i assure you that was not the case.


In fact it sounds very nonsense to me. You know you just 
came here asking on a "D FORUM" if the "D Programming Language" 
will die anytime soon...


So... expecting what? A fan confirming this?


Actually yes. Even though people here are obviously fan's of D, a 
person is still capable of giving unbiased opinion of it.
I am fan of many things i can certainly say aren't doing all that 
good and i still remain a fan.

Lots of D code

[steven kladitis via Digitalmars-d-learn]

I have 843 programs written in D. 805 actually create an 32 bit 
exe in windows 10. I am running the latest D.  Some just start to 
link and the linker disappears. Some just have issues I am  not 
able figure out. I can attach the code and scripts I use to 
compile and run these. If anyone is willing to figure out why the 
38 do not compile, I would appreciate code that works.  The 
execute_bf_v2.d creates an exe that is small but takes about 1 
hour to link on a 12 core processor with 64g of ram as 14tb of 
disk space. The rest link very fast.  If anyone is interested, 
let me know.  I would love to get the 38 working.  Also there are 
a few that produce incorrect answers.  The Generate_maze.d  
produces all but the last line of the maze.  I added a line just 
for it.  I do not understand why.  All of the programs are from 
RosettaCode.org. The  script to compile them generates a log file 
and you will see a few that the linker just stops No idea 
why. A few have 64K link errors no idea why.



TIA,
Steven

Re: MonoTime longevity

[Jonathan M Davis via Digitalmars-d-learn]

On Tuesday, December 22, 2015 15:07:58 Steven Schveighoffer via 
Digitalmars-d-learn wrote:
> MonoTime uses whatever precision is given to it by the OS. So if on your
> OS, ticksPerSecond is 1e9, then your OS clock wraps at 18 hours as well.

1e9 ticks per second should still take over 293 years to wrap around.

writeln(seconds(long.max / cast(long)1e9));

prints out

15250 weeks, 1 day, 23 hours, 47 minutes, and 16 secs

Even if the clock ticks were in picoseconds (1e12 ticks per second), the
clock would still take over 15 weeks to wrap around from 0.

The OP's

writeln(mt.ticks / mt.ticksPerSecond / 60 / 60); // prints 18 (hours)

simply indicates that the system clock thinks that 18 hours have passed
since the start of the system clock. And there's no guarantee that the
system clock starts at 0, so while it's a bit weird for it to be in the
range of 18 hours shortly after boot, it's perfectly legal. The only risk
would be if the clock started close enough to long.max to cause the clock to
wrap around even though it would have had plenty of room at 0.

So, unless I'm missing something here, there is no problem, and MonoTime
will work fine for what the OP is looking to do. As I recall, in the initial
PR for Monotime, we discussed its range based on various clock frequencies
and concluded that long was plenty large for any clock frequency we were
ever going to see; otherwise, we probably would have gone with something
similar to what POSIX uses (timespec) and split out the seconds and ticks
per second rather than simply use ticks per second.

- Jonathan M Davis

Re: : in template specialization vs constraint

[Steven Schveighoffer via Digitalmars-d-learn]

On 12/22/15 10:40 AM, Adam D. Ruppe wrote:


In specialization, it will implicitly convert, it will just select the
best match available.

Make #1:

 void func(T : ubyte)(T v) { writeln(1); }

It will then use that for for the second line because it is a *better*
match than :int, but :int still is a match so it works as a fallback.



Type specialization has some weird properties in this regard. Sometimes 
it needs to be exact or explicit, sometimes it doesn't.


http://forum.dlang.org/post/rvflnpxwzetpcphwx...@forum.dlang.org

-Steve

Re: Most performant way of converting int to string

[Steven Schveighoffer via Digitalmars-d-learn]

On 12/22/15 12:15 PM, Andrew Chapman wrote:

Sorry if this is a silly question but is the to! method from the conv
library the most efficient way of converting an integer value to a string?

e.g.
string s = to!string(100);

I'm seeing a pretty dramatic slow down in my code when I use a
conversion like this (when looped over 10 million iterations for
benchmarking).

Cheers!


Does it need to be string? What about a mutable char buffer?

If you are allocating and throwing away strings in a tight loop, simply 
reusing the buffer could save a ton of time.


Look into std.format

-Steve

Re: curl : access violation

[Ali Çehreli via Digitalmars-d-learn]

On 12/22/2015 03:10 AM, Vic wrote:

I am testing simple code in Geany (Windows 7, DMD compiler):

import std.stdio,std.net.curl;
void main()
{
// Return a char[] containing the content specified by an URL
auto content = get("dlang.org");
}

It compiled ok, but I get error after running exe file:
object.Error@(0): Access Violation





Your code works as is here: Linux, DMD64 D Compiler v2.069.0.

Ali

Re: How is D doing?

[ZombineDev via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 17:49:34 UTC, Jakob Jenkov wrote:
On Tuesday, 22 December 2015 at 03:30:32 UTC, ShinraTensei 
wrote:
I recently noticed massive increase in new languages for a 
person to jump into(Nim, Rust, Go...etc) but my question is 
weather the D is actually used anywhere or are there chances 
of it dying anytime soon.



Check out Google Trends. Searches for D Tutorial still beats 
searches for Scala Tutorial by a big margin:


https://google.com/trends/explore#q=d%20tutorial%2C%20scala%20tutorial


Google Trends shows something interesting:
https://google.com/trends/explore#q=%2Fm%2F01kbt7%2C%20%2Fm%2F0dsbpg6%2C%20%2Fm%2F091hdj%2C%20%2Fm%2F03j_q%2C%20C%2B%2B=q=Etc%2FGMT-2

Re: Most performant way of converting int to string

[Daniel Kozak via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 18:27:12 UTC, cym13 wrote:

...
I don't think there is anything in the standard
library that would really help here as (if I read it correctly) 
it is mainly
because of the conversion from ranges to arrays that this code 
is slow.


Yes, it has been faster in past, when I last check and optimeze 
to!string. But because of @nogc it has been rewriten to Range 
base version which is slower. In this case it makes sense to add 
special version without @nogc (to!string will allocate memory 
anyway) which just use dup on buffer instead of make Range.


I will probably make pull request tomorrow.

Re: Most performant way of converting int to string

[Ali Çehreli via Digitalmars-d-learn]

On 12/22/2015 10:15 AM, Andrew Chapman wrote:
> On Tuesday, 22 December 2015 at 18:11:24 UTC, rumbu wrote:

>> Converting numbers to string involves the most expensive known two
>> operations : division and modulus by 10.
>
> Cool thanks, so essentially it's unavoidable

There is hope. :)

> I have a background in PHP programming where we don't really get 
exposed to

> memory allocation, conversions etc.

You will love Andrei's recently-released presentations from code::dive 
in November 2015:


  Writing Fast Code I: https://www.youtube.com/watch?v=ph7FP0LnmcA

  Writing Fast Code II: https://www.youtube.com/watch?v=3_FXy3cT5C8

  Three Cool Things about D: https://youtube.com/watch?v=FdpaBHyQNco

The first one has an example of optimizing uint64ToAscii() at around 
1:16:30:



https://www.youtube.com/watch?feature=player_detailpage=ph7FP0LnmcA#t=4604

Ali

Re: Most performant way of converting int to string

[Ivan Kazmenko via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 18:11:24 UTC, rumbu wrote:
On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
wrote:
Sorry if this is a silly question but is the to! method from 
the conv library the most efficient way of converting an 
integer value to a string?


e.g.
string s = to!string(100);

I'm seeing a pretty dramatic slow down in my code when I use a 
conversion like this (when looped over 10 million iterations 
for benchmarking).


Cheers!


Converting numbers to string involves the most expensive known 
two operations : division and modulus by 10.


When the base is known in advance, division and modulus can be 
substituted by a few additions, subtractions and bit shifts.  For 
example, the Hacker's Delight book has a chapter dedicated to 
that, as well as a freely available additional chapter 
(www.hackersdelight.org/divcMore.pdf).


Does DMD, or Phobos function to!(string), do anything like that?  
The number of possible bases is not large anyway.  I've heard 
major C/C++ compilers do that, but have not looked for a proof 
myself.

Re: Most performant way of converting int to string

[Daniel Kozák via Digitalmars-d-learn]

V Tue, 22 Dec 2015 09:43:00 -0800
"H. S. Teoh via Digitalmars-d-learn"
 napsáno:

> On Tue, Dec 22, 2015 at 05:23:11PM +, Andrew Chapman via
> Digitalmars-d-learn wrote: [...]
> > for({int i; i = 0;} i < num; i++) {
> > //string s = to!string(i);
> > Customer c = Customer(i, "Customer", "", i
> > * 2); string result = objS.serialize(c);
> > }
> > 
> > If I uncomment the "string s" line I'm seeing a 20% increase in
> > running time, which given what's going on the rest of the code is
> > quite surprising.  I've tried compiling with both dmd and ldc2 -
> > it's the same under both.  
> [...]
> 
> I wonder if the slowdown is caused by GC collection cycles (because
> calling to!string will allocate, and here you're making a very large
> number of small allocations, which is known to cause GC performance
> issues).
> 
> Try inserting this before the loop:
> 
>   import core.memory;
>   GC.disable();
> 
> Does this make a difference in the running time?
> 
> 
> T
> 
This would  not help. It would probably be worse.

Re: Most performant way of converting int to string

[Andrew Chapman via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 17:43:00 UTC, H. S. Teoh wrote:

I wonder if the slowdown is caused by GC collection cycles 
(because calling to!string will allocate, and here you're 
making a very large number of small allocations, which is known 
to cause GC performance issues).


Try inserting this before the loop:

import core.memory;
GC.disable();

Does this make a difference in the running time?


T


Thanks!  Unfortunately that actually makes it run slightly slower 
:-)

Re: Most performant way of converting int to string

[Daniel Kozák via Digitalmars-d-learn]

V Tue, 22 Dec 2015 12:55:10 -0800
"H. S. Teoh via Digitalmars-d-learn"
 napsáno:

> On Tue, Dec 22, 2015 at 08:54:35PM +0100, Daniel Kozák via
> Digitalmars-d-learn wrote:
> > V Tue, 22 Dec 2015 09:43:00 -0800
> > "H. S. Teoh via Digitalmars-d-learn"
> >  napsáno:
> >   
> > > On Tue, Dec 22, 2015 at 05:23:11PM +, Andrew Chapman via
> > > Digitalmars-d-learn wrote: [...]  
> > > > for({int i; i = 0;} i < num; i++) {
> > > > //string s = to!string(i);
> > > > Customer c = Customer(i, "Customer",
> > > > "", i
> > > > * 2); string result = objS.serialize(c);
> > > > }
> > > > 
> > > > If I uncomment the "string s" line I'm seeing a 20% increase in
> > > > running time, which given what's going on the rest of the code
> > > > is quite surprising.  I've tried compiling with both dmd and
> > > > ldc2 - it's the same under both.
> > > [...]
> > > 
> > > I wonder if the slowdown is caused by GC collection cycles
> > > (because calling to!string will allocate, and here you're making
> > > a very large number of small allocations, which is known to cause
> > > GC performance issues).
> > > 
> > > Try inserting this before the loop:
> > > 
> > >   import core.memory;
> > >   GC.disable();
> > > 
> > > Does this make a difference in the running time?
> > > 
> > > 
> > > T
> > >   
> > This would  not help. It would probably be worse.  
> 
> I was not suggesting this as a solution, it's merely a way to
> determine whether the performance issue is GC-related.
> 
> 
> T
> 

Ok :)

Re: segfault in invariant { assert(super); }

[SimonN via Digitalmars-d-learn]

On Monday, 21 December 2015 at 20:29:14 UTC, Steven Schveighoffer 
wrote:

1) Is this recursion expected?
Yes. assert calls the virtual invariant function, which in the 
case of super is equivalent to this. So you are essentially 
calling assert(this).



2) The example is a dustmite'd version of this:
It seems like something you shouldn't do. AFAIK, invariant 
should not call any public functions on your existing class.


Thanks for the reply! Yeah, this helps for a clearer picture of 
what's happening.


In particular, even though all invariants of a class hierarchy 
are tested instead of only the most-subclassed-one, triggering 
the invariant check remains virtual. I didn't know that.


Even if Base.f() is const, it's not allowed inside 
Derived.invariant(). This is again understandable: By OOP 
principles, Derived shouldn't impose further restrictions on Base 
than what Base imposes on itself already.



(good idea to file an enhancement report).


For that, I was trying earlier today to find the exact instances 
of when there is a warning, and when there is not. I didn't get 
warnings to come up consistently. (Even the case I described in 
question 2 doens't always give a warning.) I'd have to take a 
look at this some time again.


-- Simon

Setting native OS thread name (eg, via prctl)

[Arun Chandrasekaran via Digitalmars-d-learn]

I have this trivial code where the main thread clones a child 
thread.


import std.stdio;
import core.thread;
import std.concurrency;

class DerivedThread : Thread
{
this()
{
super();
}

void quit()
{
_quit = true;
}
private:
void setOSThreadName()
{
// TODO: Is there a way to set the native OS thread name, 
worst case, via prctl?

}
void run()
{
setOSThreadName();
while(!_quit)
{
writeln("Hello from ", thisTid);
Thread.sleep(dur!("seconds")(1));
}
writeln("I'll exit now.");
}

bool _quit = false;
string _threadName = "Derived";
}

void main()
{
auto derived = new DerivedThread();
derived.start();
Thread.sleep(dur!("seconds")(4));
derived.quit();
derived.join();
}

What do i have to do to set the thread name in setOSThreadName 
(for instance, on Linux, it will reflect in proc filesystem).

Re: Setting native OS thread name (eg, via prctl)

[Arun Chandrasekaran via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 16:08:01 UTC, Dejan Lekic wrote:

Arun, isn't that what the 'name' property is there for?


Hi Dejan,

Thanks for a quick reply.

Setting the name property is not reflecting in the OS level. May 
be it is just used only at the object level?


After setting the thread name, I would like to see the it 
reflect, for instance, in the output of `top` command. You can 
press H in top to toggle threads and see their names there.


Cheers.

curl : access violation

[Vic via Digitalmars-d-learn]

I am testing simple code in Geany (Windows 7, DMD compiler):

import std.stdio,std.net.curl;
void main()
{
// Return a char[] containing the content specified by an URL
auto content = get("dlang.org");
}

It compiled ok, but I get error after running exe file:
object.Error@(0): Access Violation

Re: Socket - handling large numbers of incoming connections

[Johannes Pfau via Digitalmars-d-learn]

Am Mon, 21 Dec 2015 23:29:14 +
schrieb Adam D. Ruppe :

> On Monday, 21 December 2015 at 23:17:45 UTC, Daniel Kozák wrote:
> > If you want to reinvent the wheel you can use  
> 
> [...] it isn't like the bundled functions with the OS are 
> hard to use [...]
> 

epoll and similar interfaces are not difficult to use. But you
need to be careful to handle all error conditions caused by low level
posix io calls (read/write) correctly. (Partial reads/writes, How
do you handle EINTR? How do you handle error codes returned by the close
function*? ...)

* http://lwn.net/Articles/576478/

Re: Socket - handling large numbers of incoming connections

[Jakob Jenkov via Digitalmars-d-learn]

The same as in C [1].
Just change
#include 
to
import core.sys.posix.poll;

[1] http://linux.die.net/man/2/poll



I have a background in Java, so I am a bit handicapped :-)

Re: How is D doing?

[bachmeier via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 03:30:32 UTC, ShinraTensei wrote:
I recently noticed massive increase in new languages for a 
person to jump into(Nim, Rust, Go...etc) but my question is 
weather the D is actually used anywhere or are there chances of 
it dying anytime soon.
So far I've tried a while bunch of languages and i do like D 
the most, since i am used to C/C++ syntax also Java a bit, but 
i don't like Java.
Now i'm trying to can C/C++ and get accustomed to something 
more modern so D is my choice unless its a dead language.
I'm not looking into D for job opportunities. Just writing 
programs for my own amusement and maybe even profit some day.


I know this question has been answered, but I wanted to provide 
some hard facts for future visitors.


1. Downloads of the DMD compiler have been fluctuating between 
1000 and 1600 per day:


http://erdani.com/d/downloads.daily.png

That number only captures downloads of one compiler from one 
source.


2. Books on the language. Packt published D Cookbook in 2014. 
They have already published Learning D in 2015 and will be 
publishing D Web Development in January. Clearly, in that 
publisher's experience, D is becoming a sufficiently popular 
language to invest in it. Other books (not with that publisher) 
are currently in progress.


3. The D Language Foundation. Andrei quit his job a few months 
ago to work on D and the D Language Foundation full time.


http://forum.dlang.org/post/xsqrdgwnzehdmfmvc...@forum.dlang.org

4. The large number of participants on the main development 
forum.  Not all of them contribute, but it indicates a strong 
interest in the language to post there.

Re: Socket - handling large numbers of incoming connections

[Jakob Jenkov via Digitalmars-d-learn]

Thanks, everyone, I have looked a bit at different frameworks, 
and it seems that libasync might have a decently narrow scope to 
fit what I need.


I have a background in Java, so a lot of this OS-specific stuff 
is new to me (EPoll etc.). In Java that stuff is used under the 
hood for you, without you knowing anything about it. Java just 
chooses the best option for the given OS. This is easy to use, 
but of course gives you less control.

Re: Set color to a single point in Cairo

[Luis via Digitalmars-d-learn]

On Sunday, 20 December 2015 at 01:17:50 UTC, Basile B. wrote:

On Saturday, 19 December 2015 at 14:16:23 UTC, TheDGuy wrote:

is it possible to set the color of a single pixel with Cairo?


Not like you would do with a classic canvas (2d grid), because 
colors are applied with `cairo_fill()` and `cairo_stroke()` on 
a particular path.


but you can define a path that represents a single pixel and 
fill it:


```
cairo_rectangle (cr, x, y, 1, 1); // 1 pix rectangle
cairo_set_source_rgba (cr, 0, 0, 0, 1); // color
cairo_fill (cr); // fill the rectangle with source rgba

```

However cairo is node made to be used like this. The workflow 
is usually more based on stacked layers (1 layer = 1 path) with 
different filling, different transparency.


I did something similar here : 
https://github.com/Zardoz89/DEDCPU-16/blob/master/src/lem1802_fontview.d#L287


I need to clean these code...

Re: Setting native OS thread name (eg, via prctl)

[Dejan Lekic via Digitalmars-d-learn]

Arun, isn't that what the 'name' property is there for?

Re: Let dmd or ldc be easy to setup on Ubuntu

[Rikki Cattermole via Digitalmars-d-learn]

On 23/12/15 3:32 AM, FrankLike wrote:

On Tuesday, 22 December 2015 at 14:11:29 UTC, Rikki Cattermole wrote:

On 23/12/15 3:09 AM, FrankLike wrote:

Now,we can't setup dmd or ldc like this:
  sudo apt-get install dmd
  sudo apt-get install ldc2

If I set 'The Installation Source' is :
deb http://downloads.dlang.org/releases/2015/ main

But it's error,why?

Thank you.


dlang.org does not host a apt repository.

There is one on sourceforge for just this however.

http://d-apt.sourceforge.net/


deb http://d-apt.sourceforge.net/ trusty main

  'The Installation Source' is ok,but in Terminal it's error.
Do you have some detail about 'The Installation Source' for dmd or ldc?
Thank you.


I'm confused.
The commands listed e.g.

$ sudo wget 
http://netcologne.dl.sourceforge.net/project/d-apt/files/d-apt.list -O 
/etc/apt/sources.list.d/d-apt.list
$ sudo apt-get update && sudo apt-get -y --allow-unauthenticated install 
--reinstall d-apt-keyring && sudo apt-get update


Should work.
If it does not, please post output.

Let dmd or ldc be easy to setup on Ubuntu

[FrankLike via Digitalmars-d-learn]

Now,we can't setup dmd or ldc like this:
 sudo apt-get install dmd
 sudo apt-get install ldc2

If I set 'The Installation Source' is :
deb http://downloads.dlang.org/releases/2015/ main

But it's error,why?

Thank you.

Re: Let dmd or ldc be easy to setup on Ubuntu

[Rikki Cattermole via Digitalmars-d-learn]

On 23/12/15 3:09 AM, FrankLike wrote:

Now,we can't setup dmd or ldc like this:
  sudo apt-get install dmd
  sudo apt-get install ldc2

If I set 'The Installation Source' is :
deb http://downloads.dlang.org/releases/2015/ main

But it's error,why?

Thank you.


dlang.org does not host a apt repository.

There is one on sourceforge for just this however.

http://d-apt.sourceforge.net/

Re: Let dmd or ldc be easy to setup on Ubuntu

[FrankLike via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 14:11:29 UTC, Rikki Cattermole 
wrote:

On 23/12/15 3:09 AM, FrankLike wrote:

Now,we can't setup dmd or ldc like this:
  sudo apt-get install dmd
  sudo apt-get install ldc2

If I set 'The Installation Source' is :
deb http://downloads.dlang.org/releases/2015/ main

But it's error,why?

Thank you.


dlang.org does not host a apt repository.

There is one on sourceforge for just this however.

http://d-apt.sourceforge.net/


deb http://d-apt.sourceforge.net/ trusty main

 'The Installation Source' is ok,but in Terminal it's error.
Do you have some detail about 'The Installation Source' for dmd 
or ldc?

Thank you.

Most performant way of converting int to string

[Andrew Chapman via Digitalmars-d-learn]

Sorry if this is a silly question but is the to! method from the 
conv library the most efficient way of converting an integer 
value to a string?


e.g.
string s = to!string(100);

I'm seeing a pretty dramatic slow down in my code when I use a 
conversion like this (when looped over 10 million iterations for 
benchmarking).


Cheers!

Re: Most performant way of converting int to string

[cym13 via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
wrote:
Sorry if this is a silly question but is the to! method from 
the conv library the most efficient way of converting an 
integer value to a string?


e.g.
string s = to!string(100);

I'm seeing a pretty dramatic slow down in my code when I use a 
conversion like this (when looped over 10 million iterations 
for benchmarking).


Cheers!


Out of curiosity a slow down compared to what? No conversion at 
all?

Re: Let dmd or ldc be easy to setup on Ubuntu

[Jordi Sayol via Digitalmars-d-learn]

El 22/12/15 a les 16:38, FrankLike via Digitalmars-d-learn ha escrit:
> sudo apt-get install dmd ← it's error.

dmd_2.069.2-0-amd64.deb from http://downloads.dlang.org/ is an all-in-one deb 
package, containing all the tools and libraries for each release.

"d-lang" splits it in few deb packages:

dmd-bin (compiler and other executable files)
dmd-doc (documentation, man pages and examples)
libphobos2-69 (shared library)
libphobos2-dev (static library, symlink to shared library, module sources 
and pkg-config files)

So if you want to install dmd compiler, just type:
$ sudo apt-get install dmd-bin

Regards,
Jordi

Re: Most performant way of converting int to string

[H. S. Teoh via Digitalmars-d-learn]

On Tue, Dec 22, 2015 at 05:23:11PM +, Andrew Chapman via 
Digitalmars-d-learn wrote:
[...]
> for({int i; i = 0;} i < num; i++) {
> //string s = to!string(i);
> Customer c = Customer(i, "Customer", "", i * 2);
> string result = objS.serialize(c);
> }
> 
> If I uncomment the "string s" line I'm seeing a 20% increase in
> running time, which given what's going on the rest of the code is
> quite surprising.  I've tried compiling with both dmd and ldc2 - it's
> the same under both.
[...]

I wonder if the slowdown is caused by GC collection cycles (because
calling to!string will allocate, and here you're making a very large
number of small allocations, which is known to cause GC performance
issues).

Try inserting this before the loop:

import core.memory;
GC.disable();

Does this make a difference in the running time?


T

-- 
"Uhh, I'm still not here." -- KD, while "away" on ICQ.

Re: Most performant way of converting int to string

[Andrew Chapman via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 17:18:16 UTC, cym13 wrote:
On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
wrote:
Sorry if this is a silly question but is the to! method from 
the conv library the most efficient way of converting an 
integer value to a string?


e.g.
string s = to!string(100);

I'm seeing a pretty dramatic slow down in my code when I use a 
conversion like this (when looped over 10 million iterations 
for benchmarking).


Cheers!


Out of curiosity a slow down compared to what? No conversion at 
all?


Yeah, if I include a simple conversion in my loop:

for({int i; i = 0;} i < num; i++) {
//string s = to!string(i);
Customer c = Customer(i, "Customer", "", 
i * 2);

string result = objS.serialize(c);
}

If I uncomment the "string s" line I'm seeing a 20% increase in 
running time, which given what's going on the rest of the code is 
quite surprising.  I've tried compiling with both dmd and ldc2 - 
it's the same under both.


Cheers.

Re: How is D doing?

[Jakob Jenkov via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 03:30:32 UTC, ShinraTensei wrote:
I recently noticed massive increase in new languages for a 
person to jump into(Nim, Rust, Go...etc) but my question is 
weather the D is actually used anywhere or are there chances of 
it dying anytime soon.



Check out Google Trends. Searches for D Tutorial still beats 
searches for Scala Tutorial by a big margin:


https://google.com/trends/explore#q=d%20tutorial%2C%20scala%20tutorial

Re: Lots of D code

[Basile B. via Digitalmars-d-learn]

On Wednesday, 23 December 2015 at 00:59:53 UTC, steven kladitis 
wrote:

I have 843 programs written in D.
[...] All of the programs are from RosettaCode.org. The  script 
to compile them generates a log file and you will see a few 
that the linker just stops No idea why. A few have 64K link 
errors no idea why.



TIA,
Steven


I suggest you to put the 38 on GH (or the whole thing). They 
probably reveal some DMD bugs.

Re: Most performant way of converting int to string

[cym13 via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 17:52:52 UTC, Andrew Chapman 
wrote:

On Tuesday, 22 December 2015 at 17:43:00 UTC, H. S. Teoh wrote:

I wonder if the slowdown is caused by GC collection cycles 
(because calling to!string will allocate, and here you're 
making a very large number of small allocations, which is 
known to cause GC performance issues).


Try inserting this before the loop:

import core.memory;
GC.disable();

Does this make a difference in the running time?


T


Thanks!  Unfortunately that actually makes it run slightly 
slower :-)


I dislike guessing so here are my thought on it and the method I 
used to get there:


First I used the following code:

void f() {
import std.conv;

string s;
foreach (i ; 0..1_000_000) {
s = i.to!string;
}
}

void g() {
import core.memory;
import std.conv;

GC.disable;

string s;
foreach (i ; 0..1_000_000) {
s = i.to!string;
}
}

extern (C) int snprintf(char*, size_t, const char*, ...);
void h() {
char[10] s;
foreach (i ; 0..1_000_000) {
snprintf(cast(char*)s, 10, cast(char*)"%d", i);
}
}

void main(string[] args) {
   f;
// g;
// h;
}

Note that for h I didn't really use a string, I used a char[10]. 
We should
keep in mind that you may want to convert it to a proper string 
later.


I compiled it three times (one per function) with `dmd -profile 
-profile=gc`
and then ran it to get profiling data. I then compiled it with 
`dmd` while
timing each execution 6 times and discarding the first time (as 
the first one
has to heat the cache). The reason for the recompilation is that 
as the C
code can't be profiled and profiling puts some overhead I wanted 
to get that

off my shoulders while timing.

Here are the average times:

f: 0.50 user 0.00 system 95% CPU 0.530 total

g: 0.49 user 0.01 system 96% CPU 0.522 total

h: 0.17 user 0.00 system 92% CPU 0.188 total

The GC profiler didn't find any allocation be it in f, g or h.

The profiler was only available for f and g with very similar 
results (as

they are the same function really, here is the interesting part):

 Timer Is 3579545 Ticks/Sec, Times are in Microsecs 



  Num  TreeFuncPer
  CallsTimeTimeCall

100   390439368   265416744 265 pure nothrow 
@safe char[] std.array.array!(std.conv.toChars!(10, char, 1, 
int).toChars(int).Result).array(std.conv.toChars!(10, char, 1, 
int).toChars(int).Result)
1008322499483224994  83 pure nothrow ref 
@nogc @safe std.conv.toChars!(10, char, 1, 
int).toChars(int).Result std.conv.toChars!(10, char, 1, 
int).toChars(int).Result.__ctor(int)

2370 118276850773190160   3 _Dmain
100   52573232835191373  35 pure nothrow 
@trusted immutable(char)[] std.conv.toImpl!(immutable(char)[], 
int).toImpl(int, uint, std.ascii.LetterCase)
5904369565933204064   5 pure nothrow ref 
@nogc @safe char std.conv.emplaceRef!(char, char).emplaceRef(ref 
char, ref char)
1003274590932745909  32 pure nothrow 
char[] std.array.arrayAllocImpl!(false, char[], 
ulong).arrayAllocImpl(ulong)
100   10010158616876591  16 pure nothrow 
@nogc @safe std.conv.toChars!(10, char, 1, 
int).toChars(int).Result std.conv.toChars!(10, char, 1, 
int).toChars(int)
5901307001413070014   2 pure nothrow 
@property @nogc @safe char std.conv.toChars!(10, char, 1, 
int).toChars(int).Result.front()
1004489944412153535  12 pure nothrow 
@trusted char[] std.array.uninitializedArray!(char[], 
ulong).uninitializedArray(ulong)
5901049159510491595   1 pure nothrow ref 
@nogc @safe char 
std.conv.emplaceImpl!(char).emplaceImpl!(char).emplaceImpl(ref 
char, ref char)
690 9952971 9952971   1 pure nothrow 
@property @nogc @safe bool std.conv.toChars!(10, char, 1, 
int).toChars(int).Result.empty()
10053086148 8186704   8 pure nothrow 
@trusted char[] std.array.array!(std.conv.toChars!(10, char, 1, 
int).toChars(int).Result).array(std.conv.toChars!(10, char, 1, 
int).toChars(int).Result).__lambda2()
100   530599849 4867521   4 pure nothrow 
@safe immutable(char)[] std.conv.toImpl!(immutable(char)[], 
int).toImpl(int)
100   534801618 4201769   4 pure nothrow 
@safe immutable(char)[] 
std.conv.to!(immutable(char)[]).to!(int).to(int)
590 2520677 2520677   0 pure nothrow 
@nogc @safe void std.conv.toChars!(10, char, 1, 
int).toChars(int).Result.popFront()
100 2138919 2138919   2 pure nothrow 
@nogc @trusted char[] std.array.array!(std.conv.toChars!(10, 
char, 1, int).toChars(int).Result).array(std.conv.toChars!(10, 

Re: Most performant way of converting int to string

[rumbu via Digitalmars-d-learn]

On Tuesday, 22 December 2015 at 19:45:46 UTC, Daniel Kozák wrote:

V Tue, 22 Dec 2015 18:11:24 +
rumbu via Digitalmars-d-learn 


napsáno:

On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman 
wrote:
> Sorry if this is a silly question but is the to! method from 
> the conv library the most efficient way of converting an 
> integer value to a string?

>
> e.g.
> string s = to!string(100);
>
> I'm seeing a pretty dramatic slow down in my code when I use 
> a conversion like this (when looped over 10 million 
> iterations for benchmarking).

>
> Cheers!

Converting numbers to string involves the most expensive known 
two operations : division and modulus by 10.


No, IIRC few months or maybe years I have optimize this so it 
does not use division and modulus


It's using division and modulus, as expected:

https://github.com/D-Programming-Language/phobos/blob/master/std/conv.d#L5529

If the compiler is smart enough, maybe it will replace this by 
well known multiplication trick.