Array literals are weird.

[H. S. Teoh]

On Tue, May 04, 2021 at 06:16:15PM +0000, Q. Schroll via Digitalmars-d wrote:
> On Tuesday, 4 May 2021 at 05:24:11 UTC, Imperatorn wrote:
> > On Tuesday, 4 May 2021 at 00:34:49 UTC, Q. Schroll wrote:
> > > On Sunday, 2 May 2021 at 08:05:49 UTC, Imperatorn wrote:
> > > > Is there any way to enable this in the language?
> > > > 
> > > > ```d
> > > > auto a = [1,2,3] + [4,5,6]; //[5,7,9]
> > > > ```
[...]
> > > Alternatively, you can use `v(1, 2, 3)` instead of a slice literal.
> > 
> > Interesting! Even more cool if not the .v was required tho 😁
> 
> The operation necessitates an allocation and people here don't like
> hidden allocations.

Why would an allocation be necessary?

	struct Vec(E, size_t n) {
		E[n] impl;
		alias impl this;
	
		E[n] opBinary(string op)(Vec v) {
			Vec result;
			mixin("result.impl[] = impl[] "~op~" v.impl[];");
			return result;
		}
	}
	auto v(Args...)(Args args) {
		import std.traits : CommonType;
		alias E = CommonType!Args;
		Vec!(E, Args.length) result;
		result.impl = [ args ];
		return result;
	}
	void main() @nogc {
		// Look, ma! No allocations!
		int[3] arr = v(1,2,3) + v(4,5,6);
		assert(arr[0] == 5 && arr[1] == 7 && arr[2] == 9);
	}


T

--
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