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digitalmars.D.learn - Can You Expand Arrays into an Argument List?

reply surlymoor <surlymoor cock.li> writes:
Hello,

I don't often miss JS, but one particular feature that I enjoyed 
is the ability to expand arrays into argument lists using a unary 
operator.

Example: add(...[1, 1]) === add(1, 1) // IIRC

I've been looking in Phobos and the spec, but nothing's popped 
out to me. Is there a fairly obvious alternative to this, or am I 
going to have to experiment with some templates and mixins? (Not 
that I mind, btw, D's metaprogramming is very fun.)

With thanks,
sm
May 15 2020
parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Fri, May 15, 2020 at 06:44:52PM +0000, surlymoor via Digitalmars-d-learn
wrote:
[...]

 I don't often miss JS, but one particular feature that I enjoyed is
 the ability to expand arrays into argument lists using a unary
 operator.
 
 Example: add(...[1, 1]) === add(1, 1) // IIRC
 
 I've been looking in Phobos and the spec, but nothing's popped out to
 me. Is there a fairly obvious alternative to this, or am I going to
 have to experiment with some templates and mixins? (Not that I mind,
 btw, D's metaprogramming is very fun.)


[...]

It's possible to do it, but the called function has to support it. If
that's not an option, then you're out of luck and probably have to use
metaprogramming instead.  Here's how to do it:

	int add(int[] args...) {
		... // access `args` here as an array
	}

	void main() {
		int[] arr = [ 1, 2, 3 ];
		add(arr);
		add(1, 2);
		add(1, 3, 4, 5, 7);
	}


T

-- 
Recently, our IT department hired a bug-fix engineer. He used to work for
Volkswagen.
May 15 2020
next sibling parent Dennis <dkorpel gmail.com> writes:
On Friday, 15 May 2020 at 19:19:59 UTC, H. S. Teoh wrote:

 Here's how to do it:

 	int add(int[] args...) {
 		... // access `args` here as an array
 	}


Beware that that language feature, typesafe variadic functions, 
might become deprecated:
https://github.com/dlang/dmd/pull/11124
May 15 2020
prev sibling parent surlymoor <surlymoor cock.li> writes:
On Friday, 15 May 2020 at 19:19:59 UTC, H. S. Teoh wrote:

 It's possible to do it, but the called function has to support 
 it. If that's not an option, then you're out of luck and 
 probably have to use metaprogramming instead.  Here's how to do 
 it:

 	int add(int[] args...) {
 		... // access `args` here as an array
 	}

 	void main() {
 		int[] arr = [ 1, 2, 3 ];
 		add(arr);
 		add(1, 2);
 		add(1, 3, 4, 5, 7);
 	}


 T


Unfortunately, this isn't applicable to my situation, but I'm 
thankful nevertheless for the information. It would be nice if 
such an expansion were more universal in its applicability, but 
I'm not a language designer.

With thanks,
sm
May 15 2020