Initializing static arrays without specifying size

[bearophile]

Philippe Sigaud:

> Would a template-based solution be OK?
> 
> import std.stdio, std.traits;
> 
> CommonType!T[T.length] staticArray(T...)(T vals)
>     if ((T.length > 0) && is(CommonType!T))
> {
>     return [vals];
> }


That's one solution, but code like that is most useful when your arrays liters are long (because if they are little you can just count the items and avoid using staticArray), this is an example (I have used printf to avoid the metric ton of functions and templates used by writeln):


import std.c.stdio: printf;
import std.traits: CommonType;

CommonType!T[T.length] staticArray(T...)(T vals)
  if (T.length && is(CommonType!T)) {
    return [vals];
}

void main() {
    auto a = staticArray(0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120,
                         130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230,
                         240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340,
                         350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450,
                         460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560,
                         570, 580, 590, 600, 610, 620, 630, 640, 650, 660, 670,
                         680, 690, 700, 710, 720, 730, 740, 750, 760, 770, 780,
                         790, 800, 810, 820, 830, 840, 850, 860, 870, 880, 890,
                         900, 910, 920, 930, 940, 950, 960, 970, 980, 990);
    printf("%d\n", a[2]);
}


This is the asm of the staticArray:

_D5test2217__T11staticArrayTiÉÛÿ€€  €ÀÀ€ÈÈZÖFiiÉÛÿ€€  €¤¤ZG100i   comdat
L0:     push    EAX
        push    ESI
        push    EDI
        push    dword ptr 010h[ESP]
        push    dword ptr 018h[ESP]
        push    dword ptr 020h[ESP]
        push    dword ptr 028h[ESP]
        push    dword ptr 030h[ESP]
        push    dword ptr 038h[ESP]
        push    dword ptr 040h[ESP]
        push    dword ptr 048h[ESP]
        push    dword ptr 050h[ESP]
        push    dword ptr 058h[ESP]
        push    dword ptr 060h[ESP]
        push    dword ptr 068h[ESP]
        push    dword ptr 070h[ESP]
        push    dword ptr 078h[ESP]
        push    dword ptr 080h[ESP]
        push    dword ptr 088h[ESP]
        push    dword ptr 090h[ESP]
        push    dword ptr 098h[ESP]
        push    dword ptr 0A0h[ESP]
        push    dword ptr 0A8h[ESP]
        push    dword ptr 0B0h[ESP]
        push    dword ptr 0B8h[ESP]
        push    dword ptr 0C0h[ESP]
        push    dword ptr 0C8h[ESP]
        push    dword ptr 0D0h[ESP]
        push    dword ptr 0D8h[ESP]
        push    dword ptr 0E0h[ESP]
        push    dword ptr 0E8h[ESP]
        push    dword ptr 0F0h[ESP]
        push    dword ptr 0F8h[ESP]
        push    dword ptr 0100h[ESP]
        push    dword ptr 0108h[ESP]
        push    dword ptr 0110h[ESP]
        push    dword ptr 0118h[ESP]
        push    dword ptr 0120h[ESP]
        push    dword ptr 0128h[ESP]
        push    dword ptr 0130h[ESP]
        push    dword ptr 0138h[ESP]
        push    dword ptr 0140h[ESP]
        push    dword ptr 0148h[ESP]
        push    dword ptr 0150h[ESP]
        push    dword ptr 0158h[ESP]
        push    dword ptr 0160h[ESP]
        push    dword ptr 0168h[ESP]
        push    dword ptr 0170h[ESP]
        push    dword ptr 0178h[ESP]
        push    dword ptr 0180h[ESP]
        push    dword ptr 0188h[ESP]
        push    dword ptr 0190h[ESP]
        push    dword ptr 0198h[ESP]
        push    dword ptr 01A0h[ESP]
        push    dword ptr 01A8h[ESP]
        push    dword ptr 01B0h[ESP]
        push    dword ptr 01B8h[ESP]
        push    dword ptr 01C0h[ESP]
        push    dword ptr 01C8h[ESP]
        push    dword ptr 01D0h[ESP]
        push    dword ptr 01D8h[ESP]
        push    dword ptr 01E0h[ESP]
        push    dword ptr 01E8h[ESP]
        push    dword ptr 01F0h[ESP]
        push    dword ptr 01F8h[ESP]
        push    dword ptr 0200h[ESP]
        push    dword ptr 0208h[ESP]
        push    dword ptr 0210h[ESP]
        push    dword ptr 0218h[ESP]
        push    dword ptr 0220h[ESP]
        push    dword ptr 0228h[ESP]
        push    dword ptr 0230h[ESP]
        push    dword ptr 0238h[ESP]
        push    dword ptr 0240h[ESP]
        push    dword ptr 0248h[ESP]
        push    dword ptr 0250h[ESP]
        push    dword ptr 0258h[ESP]
        push    dword ptr 0260h[ESP]
        push    dword ptr 0268h[ESP]
        push    dword ptr 0270h[ESP]
        push    dword ptr 0278h[ESP]
        push    dword ptr 0280h[ESP]
        push    dword ptr 0288h[ESP]
        mov ECX,offset FLAT:_D14TypeInfo_G100i6__initZ
        push    dword ptr 0290h[ESP]
        push    dword ptr 0298h[ESP]
        push    dword ptr 02A0h[ESP]
        push    dword ptr 02A8h[ESP]
        push    dword ptr 02B0h[ESP]
        push    dword ptr 02B8h[ESP]
        push    dword ptr 02C0h[ESP]
        push    dword ptr 02C8h[ESP]
        push    dword ptr 02D0h[ESP]
        push    dword ptr 02D8h[ESP]
        push    dword ptr 02E0h[ESP]
        push    dword ptr 02E8h[ESP]
        push    dword ptr 02F0h[ESP]
        push    dword ptr 02F8h[ESP]
        push    dword ptr 0300h[ESP]
        push    dword ptr 0308h[ESP]
        push    dword ptr 0310h[ESP]
        push    dword ptr 0318h[ESP]
        push    dword ptr 0320h[ESP]
        push    dword ptr 0328h[ESP]
        push    064h
        push    ECX
        call    near ptr __d_arrayliteralT
        mov ESI,EAX
        mov EDI,01A0h[ESP]
        mov ECX,064h
        rep
        movsd
        add ESP,0198h
        mov EAX,8[ESP]
        pop EDI
        pop ESI
        pop ECX
        ret 0190h



And you essentially have one similar function each time you use staticArray. This is why in my answer I have said I don't know any good solution to this problem and this is why I have proposed the enhancement [$] syntax.

In my code I count the items in some way (with Python, or I assign the literal to a dynamic array, print its length and then modify the code replacing the dynamic array with the printed number).

Bye,
bearophile