Re: Write binary data as a file
On Tuesday, 2 August 2022 at 15:30:13 UTC, Adam D Ruppe wrote: On Tuesday, 2 August 2022 at 11:10:27 UTC, Alexander Zhirov wrote: As a result, I get only a set of text data. my database layer is doing to!string(that_ubyte) which is wrong. gonna see about pushing a fix It's decided! After the fix, everything works! Thank you very much!
Re: Request assistance resolving linker error: Undefined symbol(s) for architecture x86_64
On Wed, Aug 03, 2022 at 04:28:57AM +, anonymouse via Digitalmars-d-learn wrote: > How do I go about tracking down what's causing the following error: > > ``` > Undefined symbols for architecture x86_64: > "__D3std8internal6memory12__ModuleInfoZ", referenced from: > __D3loxQe12__ModuleInfoZ in dlux.o > ld: symbol(s) not found for architecture x86_64 > clang: error: linker command failed with exit code 1 (use -v to see > invocation) > ``` > > I'm not explicitly calling anything in std.internal.memory so not sure > how to resolve. Thanks. [...] This is often a sign of version mismatch between libraries and compiler. Did you recently upgrade your compiler? Did you accidentally install two versions of the standard library and the new compiler is mistakenly picking up the old library? Maybe try also recompiling your project from clean slate just in case your build process is picking up stale binaries for whatever reason. If you have object files compiled with the old version of the compiler still lying around, and they get picked up when compiling with the new compiler, it would cause link errors like the above. T -- Winners never quit, quitters never win. But those who never quit AND never win are idiots.
Request assistance resolving linker error: Undefined symbol(s) for architecture x86_64
How do I go about tracking down what's causing the following error: ``` Undefined symbols for architecture x86_64: "__D3std8internal6memory12__ModuleInfoZ", referenced from: __D3loxQe12__ModuleInfoZ in dlux.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) ``` I'm not explicitly calling anything in std.internal.memory so not sure how to resolve. Thanks. --anonymouse
How to find all modules in a package?
I want to find out all public functions in all modules in a package. Can I do that at compile time?
Re: A look inside "filter" function defintion
On Tuesday, 2 August 2022 at 14:58:52 UTC, pascal111 wrote: Maybe this helps: A template can be seen as a static struct too, so you can access its members with the scope operator "." and if there is only one member of the same name as the template ifself, the compiler auto completes it to this member. I guess you mean if we will understand the templates concept as a static struct that the template is like the struct or - "records" in Pascal - that preserve its members values each time of calling through the runtime because they are "static". Isn't like that or what do you mean? I don't know anything about Pascal - I can only say that the template scope can be seen like that from a logical point of view. A function defined in a template is a static member of that template but not necessarily static context in runtime. It depends on the usage and scope. But most library functions in Phobos are very simple like that and you have just to know that most functions are templates. They just may not require template arguments to be supplied and others do.
Re: Breaking ";" rule with lambda functions
On Tuesday, 2 August 2022 at 11:27:05 UTC, Andrey Zherikov wrote:
On Monday, 1 August 2022 at 14:15:31 UTC, pascal111 wrote:
[...]
TBH I don't find lambda syntax strange - it's pretty nice and
there are two forms (unlike in C++): short one (`a => a > 0`)
and long one (`(a) { return a > 0; }`).
[...]
Maybe I'd wrong beliefs about lambda function. It's already in
C++, so it's a traditional feature but the problem is that I
didn't use it before because I didn't study C++ yet.
Re: Write binary data as a file
On Tuesday, 2 August 2022 at 11:10:27 UTC, Alexander Zhirov wrote: As a result, I get only a set of text data. my database layer is doing to!string(that_ubyte) which is wrong. gonna see about pushing a fix
Re: Write binary data as a file
On Tue, Aug 02, 2022 at 11:10:27AM +, Alexander Zhirov via
Digitalmars-d-learn wrote:
[...]
> ```d
> auto result = db.query("select tcxs.settings_file as dbfile from
> amts.t_client_xrdp_settings tcxs where tcxs.pid_client = ?", id);
> ubyte[] bytes = cast(ubyte[])result.front()["dbfile"];
> write("newFile", bytes);
> ```
Don't use `write` for binary data. Use instead File.rawWrite:
ubyte[] data = ...;
File f = File("dbfile", "w");
f.rawWrite(data[]);
T
--
This is a tpyo.
Re: A look inside "filter" function defintion
On Tuesday, 2 August 2022 at 14:24:50 UTC, frame wrote: On Tuesday, 2 August 2022 at 12:39:41 UTC, pascal111 wrote: Instantiation seems some complicated to me. I read "If a template contains members whose name is the same as the template identifier then these members are assumed to be referred to in a template instantiation:" in the provided link, but I'm still stuck. Do you have a down-to-earth example for beginners to understand this concept? There are obvious examples direct below. Where do you get stuck? Maybe this helps: A template can be seen as a static struct too, so you can access its members with the scope operator "." and if there is only one member of the same name as the template ifself, the compiler auto completes it to this member. I guess you mean if we will understand the templates concept as a static struct that the template is like the struct or - "records" in Pascal - that preserve its members values each time of calling through the runtime because they are "static". Isn't like that or what do you mean?
Re: A look inside "filter" function defintion
On Tuesday, 2 August 2022 at 12:39:41 UTC, pascal111 wrote: Instantiation seems some complicated to me. I read "If a template contains members whose name is the same as the template identifier then these members are assumed to be referred to in a template instantiation:" in the provided link, but I'm still stuck. Do you have a down-to-earth example for beginners to understand this concept? There are obvious examples direct below. Where do you get stuck? Maybe this helps: A template can be seen as a static struct too, so you can access its members with the scope operator "." and if there is only one member of the same name as the template ifself, the compiler auto completes it to this member. You could always write out `name!(someTemplateArg).name(someRuntimeArg)`, we just prefer the short syntax `name!(someTemplateArg)(someRuntimeArg)` or `name(someRuntimeArg)` (if there are no template arguments or it could be auto deducted by the compiler). The last syntax shows that it can be called as a normal function while in fact it's a template.
Re: A look inside "filter" function defintion
On Monday, 1 August 2022 at 23:35:13 UTC, pascal111 wrote: I think this line needs explanation: '''D return FilterResult!(unaryFun!predicate, Range)(range); ''' Create an object of type `FilterResult!(unaryFun!predicate, Range)` by passing `range` to its ctor, then return that object.
Re: A look inside "filter" function defintion
On Tuesday, 2 August 2022 at 04:06:30 UTC, frame wrote: On Monday, 1 August 2022 at 23:35:13 UTC, pascal111 wrote: This is the definition of "filter" function, and I think it called itself within its definition. I'm guessing how it works? It's a template that defines the function called "Eponymous Templates": https://dlang.org/spec/template.html#implicit_template_properties A template generates code, it cannot be called, only instantiated. The common syntax is just a shortcut for using it. Otherwise you would need to write `filter!(a => a > 0).filter([1, -1, 2, 0, -3])`. Like UFCS, some magic the compiler does for you. Instantiation seems some complicated to me. I read "If a template contains members whose name is the same as the template identifier then these members are assumed to be referred to in a template instantiation:" in the provided link, but I'm still stuck. Do you have a down-to-earth example for beginners to understand this concept?
Re: Breaking ";" rule with lambda functions
On Monday, 1 August 2022 at 14:15:31 UTC, pascal111 wrote:
We all know the strange syntax of lambda function within filter
algorithm like "auto r = chain(a, b).filter!(a => a > 0);".
TBH I don't find lambda syntax strange - it's pretty nice and
there are two forms (unlike in C++): short one (`a => a > 0`) and
long one (`(a) { return a > 0; }`).
Compare to C++ lambda syntax: `[](auto a) { return a > 0; }`
My note is, don't we break D rules by leaving ";" after lambda
function syntax?!
There is no breakage: `a => a > 0` in this example is a
(template) parameter to `filter` function. You can rewrite it in
different ways, like: `filter!((a) { return a > 0; })` or
```d
alias criteria = (a) { return a > 0; };
auto r = chain(a, b).filter!criteria;
```
or even longer:
```d
auto criteria(T)(T a)
{
return a > 0;
}
auto r = chain(a, b).filter!criteria;
```
Many of D rules are taken from C, we know that, so a general
basic rule is to put ";" after each statement
I think this is more or less correct but I personally like that I
don't need to put ";" after definition of a class or struct
unlike in C.
so the previous statement of filter should be "auto r =
chain(a, b).filter!(a => a > 0;);"? Why D leaves ";" in this
case?
No. it should not. The statement here is `auto r = chain(a,
b).filter!(a => a > 0);`, not `a => a > 0`. If you use longer
version of lambda syntax then yes, you'll see ";" there: `auto r
= chain(a, b).filter!((a) { return a > 0; });` but ";" is not
after lambda function, it's inside because you have `{...}`
function body (which, I believe, is defined as a sequence of
statements so you have ";" there).
Again, both `a => a > 0` and `(a) { return a > 0; }` are just
parameters to `filter` function. Parameters are not terminated
with ";". This is the same as in C - you are not adding ";" after
function parameter:
```cpp
auto is_even = [](int i){ return i%2 == 0; };
auto result = std::find(..., ..., is_even);
```
Write binary data as a file
I'm trying to write a mechanism for writing and reading from
Postgres.
Using the Adama D. Ruppe library. I write data to Postgres in the
form of this code:
```d
ubyte[] bytes = cast(ubyte[])read("myFile");
PostgresResult resultQuery = cast(PostgresResult)
db.query("insert into amts.t_client_xrdp_settings (pid_client,
settings_file) values (?, ?)", id, bytes);
assert(resultQuery !is null);
```
Data appears in the database. Now I'm trying to do the reverse
process. Get data from Postgres and create a file:
```d
auto result = db.query("select tcxs.settings_file as dbfile from
amts.t_client_xrdp_settings tcxs where tcxs.pid_client = ?", id);
ubyte[] bytes = cast(ubyte[])result.front()["dbfile"];
write("newFile", bytes);
```
As a result, I get only a set of text data.
I am sure that my mechanism lacks refinement. It remains only to
find out which one.
Re: Converting JSONValue to AssociativeArray.
On Monday, 1 August 2022 at 22:47:03 UTC, Steven Schveighoffer
wrote:
On 8/1/22 2:00 PM, hype_editor wrote:
[...]
```d
// option 1
string[string] aa_data;
foreach(string k, v; data) {
aa_data[k] = v.get!string;
}
// option 2
import std.algorithm : map;
import std.array : assocArray;
import std.typecons : tuple;
auto aa_data = data.object
.byKeyValue
.map!(kv => tuple(kv.key, kv.value.get!string))
.assocArray;
```
I personally prefer the straightforward loop.
-Steve
Steve, thank you very much, works fine!
