• John Xu (12/12) Apr 05 2023 I saw on doc:
• Paul Backus (22/34) Apr 05 2023 Specifically, what doesn't work is initializing an associative
• John Xu (2/11) Apr 06 2023 Ok, great, thanks. Better add to the online document.
• Steven Schveighoffer (18/32) Apr 06 2023 You can get almost the same thing via a library type that duplicates the...

John Xu <728308756 qq.com> writes:

I saw on doc:
     https://dlang.org/spec/hash-map.html#static_initialization,
that map/dict/associative array, still can't be initialized like 
below:

       NOTE: Not yet implemented.

       immutable long[string] aa = [
         "foo": 5,
         "bar": 10,
         "baz": 2000
       ];

I'm wondering when this is be ready? Python can write this way 
long time ago.

Paul Backus <snarwin gmail.com> writes:

On Thursday, 6 April 2023 at 01:53:31 UTC, John Xu wrote:
 I saw on doc:
     https://dlang.org/spec/hash-map.html#static_initialization,
 that map/dict/associative array, still can't be initialized 
 like below:

       NOTE: Not yet implemented.

       immutable long[string] aa = [
         "foo": 5,
         "bar": 10,
         "baz": 2000
       ];

 I'm wondering when this is be ready? Python can write this way 
 long time ago.

Specifically, what doesn't work is initializing an associative 
array *at compile time*. You can use this syntax to initialize an 
AA at runtime, and it will work just fine.

For example:

     // Error - global variables are initialized at compile time
     long[string] globalAa = ["foo": 5, "bar": 10];

     void main()
     {
         // No error - local variables are initialized at runtime
         long[string] localAa = ["baz": 2000, "quux": 9999];
     }

To work around this limitation, you can initialize a global AA 
using a [static module constructor][1]. For example:

     long[string] globalAa;

     static this()
     {
         globalAa = ["foo": 5, "bar": 10];
     }

This will perform the initialization at runtime, during program 
startup (before calling `main`).

[1]: https://dlang.org/spec/module.html#staticorder

John Xu <728308756 qq.com> writes:

On Thursday, 6 April 2023 at 02:49:55 UTC, Paul Backus wrote:
 To work around this limitation, you can initialize a global AA 
 using a [static module constructor][1]. For example:

     long[string] globalAa;

     static this()
     {
         globalAa = ["foo": 5, "bar": 10];
     }

 This will perform the initialization at runtime, during program 
 startup (before calling `main`).

Ok, great, thanks. Better add to the online document.

Steven Schveighoffer <schveiguy gmail.com> writes:

On 4/5/23 9:53 PM, John Xu wrote:
 I saw on doc:
      https://dlang.org/spec/hash-map.html#static_initialization,
 that map/dict/associative array, still can't be initialized like below:
 
        NOTE: Not yet implemented.
 
        immutable long[string] aa = [
          "foo": 5,
          "bar": 10,
          "baz": 2000
        ];
 
 I'm wondering when this is be ready? Python can write this way long time 
 ago.

You can get almost the same thing via a library type that duplicates the 
layout of the runtime type. I did so in my `newaa` library:

https://code.dlang.org/packages/newaa

e.g.:

```d

immutable Hash!(long, string) aa = [
    "foo": 5,
    "bar": 10,
    "baz": 2000
];
```

The usage is a bit rough around the edges, I haven't implemented 
everything that is possible. But indexing works, should work for your 
use case.

But it can be cast to an AA using `asAA` (not sure about immutable 
support, I didn't test it too much).

-Steve