• Kirill (3/3) Aug 26 2021 Is there a way to do mixin or similar during runtime?
• dangbinghoo (7/10) Aug 27 2021 remember D is a statically compiled language, `mixin` is for
• Mathias LANG (6/9) Aug 27 2021 You cannot mixin at runtime. However, it is fairly easy to map a
• Kirill (20/31) Aug 27 2021 Each csv file will be different.
• jfondren (6/25) Aug 27 2021 mytuple needs to have a type that's known at compile-time, so
• Steven Schveighoffer (22/56) Aug 27 2021 So you can't build "new types" at runtime that are usable after your
• =?UTF-8?B?0JLQuNGC0LDQu9C40Lkg0KTQsNC0?= =?UTF-8?B?0LXQtdCy?= (14/17) Aug 28 2021 mixin at runtime not possible.

Kirill <kirill.saidov mail.com> writes:

Is there a way to do mixin or similar during runtime?

I'm trying to read a csv file and extract data types. Any ideas 
on how this should be approached in D are greatly appreciated.

dangbinghoo <dangbinghoo gmail.com> writes:

On Friday, 27 August 2021 at 06:52:10 UTC, Kirill wrote:
 Is there a way to do mixin or similar during runtime?

 I'm trying to read a csv file and extract data types. Any ideas 
 on how this should be approached in D are greatly appreciated.

remember D is a statically compiled language, `mixin` is for 
generating code, so, it won't work except you have a runtime code 
parser.

you may need a scripting language embedded in your D app to 
achieve this.


thx.

Mathias LANG <geod24 gmail.com> writes:

On Friday, 27 August 2021 at 06:52:10 UTC, Kirill wrote:
 Is there a way to do mixin or similar during runtime?

 I'm trying to read a csv file and extract data types. Any ideas 
 on how this should be approached in D are greatly appreciated.

You cannot mixin at runtime. However, it is fairly easy to map a 
finite and CT-know set of argument to runtime arguments via 
`static foreach`.
Could you give us example of the content of your CSV file and 
what you are trying to do ?

Kirill <kirill.saidov mail.com> writes:

On Friday, 27 August 2021 at 09:51:46 UTC, Mathias LANG wrote:
 On Friday, 27 August 2021 at 06:52:10 UTC, Kirill wrote:
 Is there a way to do mixin or similar during runtime?

 I'm trying to read a csv file and extract data types. Any 
 ideas on how this should be approached in D are greatly 
 appreciated.

 You cannot mixin at runtime. However, it is fairly easy to map 
 a finite and CT-know set of argument to runtime arguments via 
 `static foreach`.
 Could you give us example of the content of your CSV file and 
 what you are trying to do ?

Each csv file will be different.

For example:
```
name;surname;age;grade
Alex;Wong;18;87
John;Doe;19;65
Alice;Doe;18;73
etc...
```

I'd like to extract the data types automatically. For instance, 
if using tuples:
```
Tuple!(string, string, int, int) ...
```
instead I'd like to have:
```
auto mytuple = read_csv(path); // returns Tuple!(string, string, 
int, int)[]
```

jfondren <julian.fondren gmail.com> writes:

On Friday, 27 August 2021 at 10:34:27 UTC, Kirill wrote:
 Each csv file will be different.

 For example:
 ```
 name;surname;age;grade
 Alex;Wong;18;87
 John;Doe;19;65
 Alice;Doe;18;73
 etc...
 ```

 I'd like to extract the data types automatically. For instance, 
 if using tuples:
 ```
 Tuple!(string, string, int, int) ...
 ```
 instead I'd like to have:
 ```
 auto mytuple = read_csv(path); // returns Tuple!(string, 
 string, int, int)[]
 ```

mytuple needs to have a type that's known at compile-time, so 
this isn't possible. In the types are only dynamically known, 
then you have to deal in dynamic types. One way could be to have 
a read_csv that returns an array of 
https://dlang.org/phobos/std_variant.html

Steven Schveighoffer <schveiguy gmail.com> writes:

On 8/27/21 6:34 AM, Kirill wrote:
 On Friday, 27 August 2021 at 09:51:46 UTC, Mathias LANG wrote:
 On Friday, 27 August 2021 at 06:52:10 UTC, Kirill wrote:
 Is there a way to do mixin or similar during runtime?

 I'm trying to read a csv file and extract data types. Any ideas on 
 how this should be approached in D are greatly appreciated.

 You cannot mixin at runtime. However, it is fairly easy to map a 
 finite and CT-know set of argument to runtime arguments via `static 
 foreach`.
 Could you give us example of the content of your CSV file and what you 
 are trying to do ?

 
 Each csv file will be different.
 
 For example:
 ```
 name;surname;age;grade
 Alex;Wong;18;87
 John;Doe;19;65
 Alice;Doe;18;73
 etc...
 ```
 
 I'd like to extract the data types automatically. For instance, if using 
 tuples:
 ```
 Tuple!(string, string, int, int) ...
 ```
 instead I'd like to have:
 ```
 auto mytuple = read_csv(path); // returns Tuple!(string, string, int, 
 int)[]
 ```

So you can't build "new types" at runtime that are usable after your 
code is compiled. But there are options:

1. You can parse the CSV at compile-time using `import("types.csv");` 
and then processing the resulting string using CTFE (not sure if std.csv 
does this, but I'd expect it to). Then you can use the resulting thing 
to generate string mixins that can generate types. This has the drawback 
that you need to recompile when your csv input changes.

2. You can create a dynamic type that deals with the CSV data. It looks 
from your CSV data you are inferring the "type" from the data itself, 
which is complex in itself. In this case, you'd use it kind of like a 
JSON object, where you index the fields by name instead of using 
`obj.name`, and you'd have to extract the type dynamically from the type 
inference you'd have to write. This is pretty much what std.csv does, 
though you can dress it up a bit more.

Without the CSV telling you types, it's hard to make something "easy". I 
have written code that extracts from JSON data and database data 
serializable struct types, and builds a D file, but it's never 
clean-cut, and sometimes you have to hand-edit that stuff. This is about 
as "easy" as it gets, just have the computer do most of the heavy 
lifting, and then massage it into something usable.

-Steve

=?UTF-8?B?0JLQuNGC0LDQu9C40Lkg0KTQsNC0?= =?UTF-8?B?0LXQtdCy?= writes:

On Friday, 27 August 2021 at 06:52:10 UTC, Kirill wrote:
 Is there a way to do mixin or similar during runtime?

 I'm trying to read a csv file and extract data types. Any ideas 
 on how this should be approached in D are greatly appreciated.

mixin at runtime not possible.
Source code compilation and runing in runtime not possible. But!

But you can impement this!

Steps:
1. Need D compiller
2. In runtime you can compile mixin to dynamic library (.so or 
.dll) using  external command: `dmd ...`
3. Load dynamic library using `dlopen()` `dlsym()` `dlclose()`. 
(on Windows: LoadLibrary(), GetProcAdres(), FreLibrary())
4. Call mixin functions, variables
5. Done!

Packages bindbc-*, derelict-* uses dynamic loading. You can use 
both as examples.