Random Access I/O
I need to be able to perform random access I/O against a file, creating a new file if it doesn't exist, or opening as-is (no truncation) if it already exists. None of the access modes for std.stdio.File seem to allow that. Any usage of the "w" mode causes my code to consider the file empty if it pre-exists (though, it doesn't always actually truncate the disk on file?) If I was coding in C, I would use open() as it gives more options for access: http://pubs.opengroup.org/onlinepubs/009695399/functions/open.html However, I don't see this exposed in phobos anywhere?
Static convertability testing?
I have a template function that gets values out of a tree of
variant types. My goal is to be able to write code like;
node.get!string(path, to, leaf);
Inside get(), I would like to use std.conv to dynamically convert
(where able) to the target type (T) or, if that is not possible,
to return T.init.
If I wanted to force the user to request the correct type as is
stored in the structure, I could write code like:
switch (leafType) {
case STRING:
static if (is(T : string)) {
return leftValue;
}
else {
return T.init
}
break;
...
But since I want to allow all possiblities that std.conv
supports, I want something like:
static if (isConvertible!(T, string)) {
return leftValue.to!T;
}
else {
return T.init;
}
Is there something like isConvertible() in the library somewhere?
Re: Time from timestamp?
On Friday, 30 January 2015 at 22:22:27 UTC, Rikki Cattermole wrote: On a slightly related note, I have code for UTC+0 to unix time stamp. https://github.com/Devisualization/util/blob/b9ab5758e755c4e33832ac4aed0a5d7f2c728faf/source/core/devisualization/util/core/time.d Unix timestamps can be negative, so you should probably be using longs instead of ulongs.
Time from timestamp?
I'm attempting to print a human-readable version of a timestamp.
The timestamp is coming from an external service, via JSON. An
example is:
1421865781342
Which I know to be:
2015-01-21T18:43:01.342Z
The only method I see which takes an epoch-style timestamp, so
that I can convert it to something printable, is the SysTime
constructor:
pure nothrow @safe this(long stdTime, immutable TimeZone tz =
null);
According to the reference, this seems to take the value in
hnsecs. My expectation would be that this means multiplying my
initial value by 1_000_000. But if I do that, I get a random date
2500 years in the future.
I created this sample code:
void main() {
long time = 1421865781342L;
writefln(%s, SysTime(time));
writefln(%s, SysTime(time * 10L));
writefln(%s, SysTime(time * 100L));
writefln(%s, SysTime(time * 1_000L));
writefln(%s, SysTime(time * 10_000L));
writefln(%s, SysTime(time * 100_000L));
writefln(%s, SysTime(time * 1_000_000L));
writefln(%s, Clock.currTime.stdTime);
}
Outputs:
0001-Jan-02 07:36:48.5781342
0001-Jan-17 03:04:47.781342
0001-Jun-14 05:44:39.81342
0005-Jul-04 08:23:20.1342
0046-Jan-21 10:50:03.342
0451-Jul-28 11:17:15.42
4506-Sep-18 16:42:14.2
635582516
My expectation would be that the final line would be something
beginning with 14 at least. Playing around with possible
multipliers, there doesn't even seem to be any integer value that
would allow conversion between the timestamp I received and
whatever SysTime expects.
I'm using:
DMD64 D Compiler v2.066.1
Ubuntu from .deb package
Is this a bug, or am I doing something wrong?
Re: Time from timestamp?
On Saturday, 31 January 2015 at 00:20:07 UTC, ketmar wrote: On Sat, 31 Jan 2015 00:03:43 +, Chris Williams wrote: since most database software probably stores birthdates (many of which are pre-1970) in this format O_O a perfectly broken software. And stdc: http://h50146.www5.hp.com/products/software/oe/tru64unix/manual/v51a_ref/HTML/MAN/MAN3/3955.HTM And UNIX: http://www.lehman.cuny.edu/cgi-bin/man-cgi?mktime+3
Re: Time from timestamp?
On Friday, 30 January 2015 at 22:38:21 UTC, Chris Williams wrote: On Friday, 30 January 2015 at 22:22:27 UTC, Rikki Cattermole wrote: On a slightly related note, I have code for UTC+0 to unix time stamp. https://github.com/Devisualization/util/blob/b9ab5758e755c4e33832ac4aed0a5d7f2c728faf/source/core/devisualization/util/core/time.d Unix timestamps can be negative, so you should probably be using longs instead of ulongs. Yup, there was a world before January 1st, 1970.
Re: Time from timestamp?
On Friday, 30 January 2015 at 23:50:53 UTC, ketmar wrote: On Fri, 30 Jan 2015 23:42:04 +, Chris Williams wrote: On Friday, 30 January 2015 at 22:38:21 UTC, Chris Williams wrote: On Friday, 30 January 2015 at 22:22:27 UTC, Rikki Cattermole wrote: On a slightly related note, I have code for UTC+0 to unix time stamp. https://github.com/Devisualization/util/blob/ b9ab5758e755c4e33832ac4aed0a5d7f2c728faf/source/core/devisualization/util/ core/time.d Unix timestamps can be negative, so you should probably be using longs instead of ulongs. Yup, there was a world before January 1st, 1970. not for unix timestamps. please, stop that, unix timestamp was not designed to present any dates before 1970. negative timestamp is a bug in code. Unless you know something I don't, everything I've ever read says that a negative unix timestamp is meant to refer to a time before 1970. It may not have been intentional, but since most database software probably stores birthdates (many of which are pre-1970) in this format, having a library be unable to support them just makes the library useless for many situations.
Re: Time from timestamp?
On Saturday, 31 January 2015 at 00:14:37 UTC, Steven
Schveighoffer wrote:
On 1/30/15 5:18 PM, Chris Williams wrote:
I'm attempting to print a human-readable version of a
timestamp. The
timestamp is coming from an external service, via JSON. An
example is:
1421865781342
Which I know to be:
2015-01-21T18:43:01.342Z
http://dlang.org/phobos/std_datetime.html#.unixTimeToStdTime
It's kind of convoluted because there is no epoch, but you can
make one:
import std.datetime;
import std.stdio;
void main(string[] args)
{
// can't make this enum because of time zone...
auto epoch = SysTime(unixTimeToStdTime(0), UTC());
writeln(epoch + 1_421_865_781_342.msecs);
}
output:
2015-Jan-21 18:43:01.342Z
Note the reason your code didn't work is because SysTime uses
1/1/1 as the epoch.
-Steve
D'oh, I missed that in the description:
and convert it to hnsecs in UTC since midnight, January 1st, 1
A.D. UTC
That does explain it. I also didn't spot the declaration of
unixTimeToStdTime(), which assuredly helps.
Thank you!
Re: How to copy object of class A to another object of class B?
On Wednesday, 28 January 2015 at 09:44:29 UTC, zhmt wrote:
Sometime , I need to copy them:
thrift.Card tc;
db.Card dc;
dc.id = tc.id;
dc.pwd = tc.pwd;
...
It is boring coding, I want a solution to copy them
automatically:
void copyObj(SRC,DEST)(SRC src,DEST dest)
{
foreach (i, type; typeof(SRC.tupleof)) {
auto name = SRC.tupleof[i].stringof;
__traits(getMember, dest, name) = __traits(getMember, src,
name);
writeln(name);
}
}
Unfortunitely, it doesnt work, how to improve it?
Assuming that the hibernated class isn't auto-generated and you
can redefine its contents freely, the following style may be an
alternative that works for you:
struct Foo {
public:
string a;
int b;
}
class FooClass {
public:
union {
struct {
string a;
int b;
};
Foo foo;
}
}
void main() {
Foo f = Foo(a, 10);
FooClass c = new FooClass();
c.foo = f;
writefln(%s %s, c.a, c.b);
}
Probably the anonymous struct will break the UDAs, but it should
be worth testing.
Re: Using std.net.curl to stream data
On Wednesday, 28 January 2015 at 14:18:38 UTC, Trollgeir wrote:
I'm having some trouble trying to stream data to my plot.ly
graph:
https://plot.ly/62/~Trollgeir/
The API: https://plot.ly/streaming/
I am able to post messages that get recorded into the stream
live, although right after curl uploads it, it just seems to
wait for a response it's not getting, and eventually timeouts.
Does anyone have any advice?
auto client = HTTP(stream.plot.ly);
client.addRequestHeader(plotly-streamtoken,e8bg6omat6);
client.verbose = true;
string msg = { \x\: 500, \y\: 500 } \n;
client.postData(msg);
client.perform;
You have to define a handler for HTTP.onReceive before calling
HTTP.perform. It will receive ubyte arrays for each packet that
comes in. For most purposes, you just copy that onto the end of a
string in an external scope. But if you're streaming content,
you'll need to do something more fancy.
Re: how convert the range to slice ?
On Wednesday, 28 January 2015 at 22:43:36 UTC, bearophile wrote: Nordlöw: Is there any chance we could add logic to dmd+phobos that hints user about this? It's such a fundamental part of D+Phobos that newbies are forced to learn this quickly. On the other hand an informative error message could be useful... What error message do you suggest? Bye, bearophile Range is not castable to array. See std.array.array to generate an array from a Range.
Re: Russian translation of the range term?
On Wednesday, 12 November 2014 at 11:38:52 UTC, thedeemon wrote: On Tuesday, 11 November 2014 at 11:50:18 UTC, Ivan Kazmenko wrote: Hi! I'm unsure what is the Russian equivalent for the term range, as in D range, the generalization of a pair of iterators. I think последовательность (sequence) is the most appropriate, because the defining characteristic of an input range (most common one) is ability to provide data sequentially. Also, afaik, some languages like F# and Clojure use this term (often shortened to 'seq') for the same thing that D calls ranges. While sequence makes more sense for how std.range thinks of ranges, I think the history of the term is closer to how we use slices. So another (English) alternative to try might be a view. It's a fairly common term in SQL databases, so presumably there's a translation for it in Russian.
Re: Why do some language-defined attributes have @ and some not?
On Thursday, 23 October 2014 at 07:39:21 UTC, Gary Willoughby wrote: On Thursday, 23 October 2014 at 00:59:26 UTC, Shriramana Sharma via Digitalmars-d- I submit that the syntax for attributes should be streamlined. Shall I go and open a Bugzilla item? No need: http://wiki.dlang.org/DIP64 Besides the @ symbols, isn't there also some inconsistency on whether attributes go before or after the declaration? @property public static void foo() const @safe pure nothrow I've never bothered to ascertain how much of the positioning is optional, but definitely none of it makes sense.
Re: Search Engine
On Wednesday, 8 October 2014 at 18:15:08 UTC, ANtlord wrote: It would be stable? I mean program, that will use C++ extern interface. Trying to link to C++ code will cause some work to solve build issues, but there shouldn't be any stability impacts other than recognizing that C++ won't be using memory management.
Re: Momentary Eh?! for a Dynamic Language Programmmer. Tuples vs Arrays. Just rambling.
On Monday, 23 June 2014 at 22:08:59 UTC, John Carter wrote: On Monday, 23 June 2014 at 21:26:19 UTC, Chris Williams wrote: More likely what you want are variants: Hmm. Interesting. Yes, Variant and VariantArray are much closer to the dynamic language semantics... But the interesting thing is Tuple is much closer to What I Mean when I create these things. I probably should used Rubies http://ruby-doc.org/core-2.0/Struct.html but apart from naming the elements it gives me nothing beyond more keystrokes to enter. Tuple is very similar, but also grants type safety. D has structs. If you have any problem working with Tuples, you might consider moving over.
Re: Momentary Eh?! for a Dynamic Language Programmmer. Tuples vs Arrays. Just rambling.
On Monday, 23 June 2014 at 21:18:39 UTC, John Carter wrote: I guess between perl and Ruby and Scheme etc. I got used to creating hybrid containers Want a pair of [string, fileList]? Just make an Array with two items, one a string, one and array of strings. Done. D barfed... leaving me momentarily stunned... then Oh Yes, type safety, Tuple's are the answer where Tuples where Tuples... Eventually found http://dlang.org/tuple.html and more specifically the somewhat unexpectedly named http://dlang.org/phobos/std_typecons.html and off I went... I do have a personal design guideline of when you adding too much behaviour to a heterocontainer, refactor into a class. But I guess I have never realised how often I do casually create heterogenous containers Just rambling and musing. More likely what you want are variants: http://dlang.org/library/std/variant/variantArray.html http://dlang.org/library/std/variant.html Tuples can hold multiple types, but they're only available during compile time.
Separate allocation and construction?
If I wanted to allocate memory for a class and then call its
constructor as two separate steps, while still having the object
be managed by the garbage collector, is there any way to do that?
I believe that I've figured out a way to accomplish the first
step, but not the second.
import std.stdio;
class Foo {
this(string bar) {
writeln(bar);
}
}
void main() {
Foo f = (new Foo[1])[0];
f(Hello); // doesn't compile
}
Re: Separate allocation and construction?
On Thursday, 5 June 2014 at 22:25:03 UTC, Adam D. Ruppe wrote: On Thursday, 5 June 2014 at 22:22:16 UTC, Chris Williams wrote: If I wanted to allocate memory for a class and then call its constructor as two separate steps, while still having the object be managed by the garbage collector, is there any way to do that? Check out std.conv.emplace http://dlang.org/phobos/std_conv.html#emplace First, allocate the memory block for the class. The size is __traits(classInstanceSize, Yourclass). Then slice it: enum size = __traits(classInstanceSize, YourClass); auto memory = GC.malloc(size)[0 .. size]; Why slice? There seems to be a version of emplace that accepts a pointer, which is what GC.malloc() seems to return.
