DIP 1019--Named Arguments Lite--Community Review Round 1

[Atila Neves]

On Monday, 18 February 2019 at 13:18:15 UTC, Rubn wrote:
> On Monday, 18 February 2019 at 10:17:32 UTC, Atila Neves wrote:
>> On Friday, 15 February 2019 at 17:43:52 UTC, 12345swordy wrote:
>>> On Friday, 15 February 2019 at 17:38:23 UTC, Francesco Mecca 
>>> wrote:
>>>> On Friday, 15 February 2019 at 13:49:04 UTC, Atila Neves 
>>>> wrote:
>>>>> [...]
>>>>
>>>> I think that the solution proposed by Atila is better for 
>>>> the following reasons:
>>>> 1. it is a library solution
>>>> 2. allows both the user and the author of a library to 
>>>> specify functions with named parameters
>>>> 3. it is very lightweight
>>>>
>>>> [...]
>>>
>>> You miss the other reason on why it is not enough: Compile 
>>> time and run-time performance penalty.
>>> -Alex
>>
>> Run-time? I'd expect the call to inlined. It'll definitely 
>> take longer to compile though, but I'm at a loss why named 
>> parameters in the compiler are expected to be free.
>
> The compiler isn't some magic device, your implementation is 
> not easily optimized out to have no runtime cost. Even LDC has 
> trouble optimizing it, and forget about DMD.
>
> struct Foo {
>     int[1024] value;
> }

<snip>

Good shout, thanks for bringing that up. I fixed this in version 
0.0.2 (just pushed), and now both `callSlowFoo` and `callFastFoo` 
below yield the exact same assembly with ldc, and the function 
calls were inlined:

----------------------------------------------
import kwargs;

struct Foo {
     int[1024] value;
}

void fastFoo(ref Foo faa) {
     import core.stdc.stdio: printf;
     foreach(int i, ref v; faa.value) {
         printf("%d ", v);
     }
     printf("\n");
  }

alias slowFoo = kwargify!fastFoo;


void callSlowFoo() {
     Foo foo;
     initFoo(foo);
     slowFoo(foo);
}

void callFastFoo() {
     Foo foo;
     initFoo(foo);
     fastFoo(foo);
}

void initFoo(ref Foo foo) {
     foreach(int i, ref v; foo.value) {
         v = i;
     }
}

void main() {
     callSlowFoo;
     // callFastFoo; // it's the same!
}

----------------------------------------------