digitalmars.D.learn - Associative Array, get value instead of poiter using `if (auto ..)`,

ryuukk_ (12/12) Aug 31 ```D

Steven Schveighoffer (3/15) Aug 31 Maybe if(auto it = test.get(“hello”, 0))

ryuukk_ (3/22) Aug 31 Now i can't use 0 as a value, that's not a solution

kdevel (3/27) Sep 01 Shall the if clause evaluate as true if the value of the AA

Paul Backus (23/35) Aug 31 Once the next release of Phobos comes out, with [PR 9039][1]

ryuukk_ (5/44) Aug 31 See, that's the thing i hate about D, solving simple problem

ryuukk_ (14/14) Aug 31 Let's see how other languages do it:

Lance Bachmeier (2/16) Aug 31 It's good you're not in charge here because that is hideous.

ryuukk_ (5/26) Aug 31 Paul Backup solution is infinity better, i apologies
Richard (Rikki) Andrew Cattermole (3/25) Aug 31 Hey now, there is no need to get personal, ryuukk is evaluating out

Nick Treleaven (16/29) Sep 02 We don't have `if` callback syntax, but essentially you can do

Nick Treleaven (2/4) Sep 02 https://issues.dlang.org/show_bug.cgi?id=24255
Nick Treleaven (4/7) Sep 02 Sorry, that aborts if the key isn't present. `update` requires

kdevel (14/36) Aug 31 Is that functionally different from

Paul Backus (7/19) Aug 31 It's essentially the same. I only suggested it because the

ryuukk_ (30/54) Sep 01 you are wrong, the question wasn't about "an alternative to

evilrat (20/27) Sep 01 An alternative would be yet another template wrapper for get

ryuukk_ <ryuukk.dev gmail.com> writes:

```D
void main()
{
     int[string] test;

     test["hello"] = 42;

     if (auto it = "hello" in test)
     {

     }

}
```
Is there a way to get the value instead of a pointer? while 
keeping the conciseness (one line)

Aug 31

Steven Schveighoffer <schveiguy gmail.com> writes:

On Saturday, 31 August 2024 at 12:47:25 UTC, ryuukk_ wrote:
 ```D
 void main()
 {
     int[string] test;

     test["hello"] = 42;

     if (auto it = "hello" in test)
     {

     }

 }
 ```
 Is there a way to get the value instead of a pointer? while 
 keeping the conciseness (one line)

Maybe if(auto it = test.get(“hello”, 0))

-Steve

Aug 31

ryuukk_ <ryuukk.dev gmail.com> writes:

On Saturday, 31 August 2024 at 13:00:42 UTC, Steven Schveighoffer 
wrote:
 On Saturday, 31 August 2024 at 12:47:25 UTC, ryuukk_ wrote:
 ```D
 void main()
 {
     int[string] test;

     test["hello"] = 42;

     if (auto it = "hello" in test)
     {

     }

 }
 ```
 Is there a way to get the value instead of a pointer? while 
 keeping the conciseness (one line)

 Maybe if(auto it = test.get(“hello”, 0))

 -Steve

Now i can't use 0 as a value, that's not a solution

Aug 31

kdevel <kdevel vogtner.de> writes:

On Saturday, 31 August 2024 at 13:48:52 UTC, ryuukk_ wrote:
 On Saturday, 31 August 2024 at 13:00:42 UTC, Steven 
 Schveighoffer wrote:
 On Saturday, 31 August 2024 at 12:47:25 UTC, ryuukk_ wrote:
 ```D
 void main()
 {
     int[string] test;

     test["hello"] = 42;

     if (auto it = "hello" in test)
     {

     }

 }
 ```
 Is there a way to get the value instead of a pointer? while 
 keeping the conciseness (one line)

 Maybe if(auto it = test.get(“hello”, 0))

 -Steve

 Now i can't use 0 as a value, that's not a solution

Shall the if clause evaluate as true if the value of the AA 
lookup coerces to false (and vice versa)?

Sep 01

Paul Backus <snarwin gmail.com> writes:

On Saturday, 31 August 2024 at 12:47:25 UTC, ryuukk_ wrote:
 ```D
 void main()
 {
     int[string] test;

     test["hello"] = 42;

     if (auto it = "hello" in test)
     {

     }

 }
 ```
 Is there a way to get the value instead of a pointer? while 
 keeping the conciseness (one line)

Once the next release of Phobos comes out, with [PR 9039][1] 
merged, you'll be able to do it like this:

```d
import std.typecons;

Nullable!V maybeGet(K, V)(V[K] aa, K key)
{
     if (auto ptr = key in aa)
         return nullable(*ptr);
     else
         return Nullable!V.init;
}

void main()
{
     import std.stdio;

     int[string] test = ["hello": 42];

     if (auto it = test.maybeGet("hello"))
     {
         writeln("hello => ", it.get);
     }
}
```

[1]: https://github.com/dlang/phobos/pull/9039

Aug 31

ryuukk_ <ryuukk.dev gmail.com> writes:

On Saturday, 31 August 2024 at 14:25:29 UTC, Paul Backus wrote:
 On Saturday, 31 August 2024 at 12:47:25 UTC, ryuukk_ wrote:
 ```D
 void main()
 {
     int[string] test;

     test["hello"] = 42;

     if (auto it = "hello" in test)
     {

     }

 }
 ```
 Is there a way to get the value instead of a pointer? while 
 keeping the conciseness (one line)

 Once the next release of Phobos comes out, with [PR 9039][1] 
 merged, you'll be able to do it like this:

 ```d
 import std.typecons;

 Nullable!V maybeGet(K, V)(V[K] aa, K key)
 {
     if (auto ptr = key in aa)
         return nullable(*ptr);
     else
         return Nullable!V.init;
 }

 void main()
 {
     import std.stdio;

     int[string] test = ["hello": 42];

     if (auto it = test.maybeGet("hello"))
     {
         writeln("hello => ", it.get);
     }
 }
 ```

 [1]: https://github.com/dlang/phobos/pull/9039

See, that's the thing i hate about D, solving simple problem 
requires templates + import + function call

I already lost interest, i'll solve that problem with something 
else

Aug 31

ryuukk_ <ryuukk.dev gmail.com> writes:

Let's see how other languages do it:

```zig
     map.put("hello", 42);

     // get pointer
     if (map.get("hello")) |*it| {
         std.log.debug("{}", .{it});
     }

     // get value
     if (map.get("hello")) |it| {
         std.log.debug("{}", .{it});
     }
```

No imports, no templates, ONE LINER

Please submit PRs to DMD, not phobos

Aug 31

Lance Bachmeier <no spam.net> writes:

On Saturday, 31 August 2024 at 15:38:49 UTC, ryuukk_ wrote:
 Let's see how other languages do it:

 ```zig
     map.put("hello", 42);

     // get pointer
     if (map.get("hello")) |*it| {
         std.log.debug("{}", .{it});
     }

     // get value
     if (map.get("hello")) |it| {
         std.log.debug("{}", .{it});
     }
 ```

 No imports, no templates, ONE LINER

 Please submit PRs to DMD, not phobos

It's good you're not in charge here because that is hideous.

Aug 31

ryuukk_ <ryuukk.dev gmail.com> writes:

On Saturday, 31 August 2024 at 16:34:00 UTC, Lance Bachmeier 
wrote:
 On Saturday, 31 August 2024 at 15:38:49 UTC, ryuukk_ wrote:
 Let's see how other languages do it:

 ```zig
     map.put("hello", 42);

     // get pointer
     if (map.get("hello")) |*it| {
         std.log.debug("{}", .{it});
     }

     // get value
     if (map.get("hello")) |it| {
         std.log.debug("{}", .{it});
     }
 ```

 No imports, no templates, ONE LINER

 Please submit PRs to DMD, not phobos

 It's good you're not in charge here because that is hideous.

Paul Backup solution is infinity better, i apologies

I'll now leave, just like everyone else, sorry for the noise, who 
am i to expect improvements, i should have known better

Aug 31

"Richard (Rikki) Andrew Cattermole" <richard cattermole.co.nz> writes:

On 01/09/2024 4:34 AM, Lance Bachmeier wrote:
 On Saturday, 31 August 2024 at 15:38:49 UTC, ryuukk_ wrote:
 Let's see how other languages do it:

 ```zig
     map.put("hello", 42);

     // get pointer
     if (map.get("hello")) |*it| {
         std.log.debug("{}", .{it});
     }

     // get value
     if (map.get("hello")) |it| {
         std.log.debug("{}", .{it});
     }
 ```

 No imports, no templates, ONE LINER

 Please submit PRs to DMD, not phobos

 
 It's good you're not in charge here because that is hideous.

Hey now, there is no need to get personal, ryuukk is evaluating out 
ideas and there is nothing wrong with this.

Aug 31

Nick Treleaven <nick geany.org> writes:

On Saturday, 31 August 2024 at 15:38:49 UTC, ryuukk_ wrote:
 Let's see how other languages do it:

 ```zig
     map.put("hello", 42);

     // get pointer
     if (map.get("hello")) |*it| {
         std.log.debug("{}", .{it});
     }

     // get value
     if (map.get("hello")) |it| {
         std.log.debug("{}", .{it});
     }
 ```
 No imports, no templates, ONE LINER

We don't have `if` callback syntax, but essentially you can do 
that:
```d
void main()
{
     int[string] test;

     test["hello"] = 42;
     test.update("hello", () => noreturn.init, (ref int x) {
         x++;
     });
     assert(test["hello"] == 43);
}
```

Omit the `ref` if you want a copy of the value. Annoyingly, the 
`int` is required, though maybe just an IFTI bug.

Sep 02

Nick Treleaven <nick geany.org> writes:

On Monday, 2 September 2024 at 11:56:10 UTC, Nick Treleaven wrote:
 Annoyingly, the `int` is required, though maybe just an IFTI 
 bug.

https://issues.dlang.org/show_bug.cgi?id=24255

Sep 02

Nick Treleaven <nick geany.org> writes:

On Monday, 2 September 2024 at 11:56:10 UTC, Nick Treleaven wrote:
     test.update("hello", () => noreturn.init, (ref int x) {
         x++;
     });

Sorry, that aborts if the key isn't present. `update` requires 
the first callback to provide a value for the key, and it can't 
return void.

Sep 02

kdevel <kdevel vogtner.de> writes:

On Saturday, 31 August 2024 at 14:25:29 UTC, Paul Backus wrote:
 [...]
 Once the next release of Phobos comes out, with [PR 9039][1] 
 merged, you'll be able to do it like this:

 ```d
 import std.typecons;

 Nullable!V maybeGet(K, V)(V[K] aa, K key)
 {
     if (auto ptr = key in aa)
         return nullable(*ptr);
     else
         return Nullable!V.init;
 }

 void main()
 {
     import std.stdio;

     int[string] test = ["hello": 42];

     if (auto it = test.maybeGet("hello"))
     {
         writeln("hello => ", it.get);
     }
 }
 ```

Is that functionally different from

```
void main()
{
     import std.stdio;

     int[string] test = ["hello": 42];

     if (auto p = "hello" in test)
     {
         writeln("hello => ", *p);
     }
}
```

?

Aug 31

Paul Backus <snarwin gmail.com> writes:

On Saturday, 31 August 2024 at 22:06:26 UTC, kdevel wrote:
 Is that functionally different from

 ```
 void main()
 {
     import std.stdio;

     int[string] test = ["hello": 42];

     if (auto p = "hello" in test)
     {
         writeln("hello => ", *p);
     }
 }
 ```

It's essentially the same. I only suggested it because the 
original question was about alternatives to pointers, and 
`Nullable` isn't a pointer.

I suppose it goes to show that avoiding language features just 
for the sake of it ("no pointers", "no templates", "no imports", 
...) is unlikely to accomplish anything useful. :)

Aug 31

ryuukk_ <ryuukk.dev gmail.com> writes:

On Sunday, 1 September 2024 at 03:06:53 UTC, Paul Backus wrote:
 On Saturday, 31 August 2024 at 22:06:26 UTC, kdevel wrote:
 Is that functionally different from

 ```
 void main()
 {
     import std.stdio;

     int[string] test = ["hello": 42];

     if (auto p = "hello" in test)
     {
         writeln("hello => ", *p);
     }
 }
 ```

 It's essentially the same. I only suggested it because the 
 original question was about alternatives to pointers, and 
 `Nullable` isn't a pointer.

you are wrong, the question wasn't about "an alternative to 
pointer"

i'll quote myself:

 Is there a way to get the value instead of a pointer? while 
 keeping the conciseness (one line)

this is not asking for an "alternative"

if i have to call `.get` or dereference the pointer myself, the 
premise of "conciseness and one liner" is lost

i pasted a simple example so everyone understands the task, my 
actual use case is more complex and longer


 I suppose it goes to show that avoiding language features just 
 for the sake of it ("no pointers", "no templates", "no 
 imports", ...) is unlikely to accomplish anything useful. :)

you didn't understand the question, so why assume this?

if checking for/getting a value from a hashmap requires all that 
crap, then perhaps something is wrong with the language, and it 
perhaps isn't the one i should have picked for the task

my mistake perhaps, not yours


besides, i do use the language features in my project, templates 
and mixins to solve larger problems, it's great, and reason why i 
picked D

another thing people don't understand:

```
$ time make build-game

real    0m0.402s
user    0m0.352s
sys     0m0.050s
```

i value this too, more than anything else, and i like good error 
messages

i don't like cryptic error messages and 10+ seconds build times

i won't bother reading this thread, as i said, i lost interest, 
if you can't understand what an improvement is from a user PoV, 
then there is nothing else for me to say

Sep 01

evilrat <evilrat666 gmail.com> writes:

On Sunday, 1 September 2024 at 08:50:53 UTC, ryuukk_ wrote:
 if checking for/getting a value from a hashmap requires all 
 that crap, then perhaps something is wrong with the language, 
 and it perhaps isn't the one i should have picked for the task

 my mistake perhaps, not yours


 besides, i do use the language features in my project, 
 templates and mixins to solve larger problems, it's great, and 
 reason why i picked D


An alternative would be yet another template wrapper for get 
value that takes a dictionary an a lambda and call that lambda 
only if value is present, this means you no longer do the if, but 
rather a "cryptic" call like in some other languages.

pseudo code:
```d
// helper function
void withKey(V,K,L)(V[K] dict, K key, lazy L dostuff) {
     if (auto value = dict.get(K)) {
         doStuff(*value);
     }
}

// usage

string[int] counters;
counters["foo"] = 42;
counters.withKey("foo", (value) {
     assert(value == 42);
});
```

Sep 01

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digitalmars.D.learn - Associative Array, get value instead of poiter using `if (auto ..)`,