Is it possible to filter variadics?

[maik klein via Digitalmars-d-learn]

On Wednesday, 4 November 2015 at 06:20:30 UTC, Jakob Ovrum wrote:
> On Tuesday, 3 November 2015 at 23:41:10 UTC, maik klein wrote:
>> [...]
>
> import std.algorithm.iteration : sum;
> import std.meta : allSatisfy, Filter;
> import std.traits;
> import std.typecons : tuple;
> import std.range : only;
>
> // These two are necessary since the ones in std.traits
> // don't accept non-types
> enum isIntegral(alias i) = std.traits.isIntegral!(typeof(i));
> enum isFloatingPoint(alias f) = 
> std.traits.isFloatingPoint!(typeof(f));
>
> auto separateSum(T...)(T args)
> 	if(allSatisfy!(isNumeric, T))
> {
> 	return tuple(only(Filter!(isIntegral, args)).sum(), 
> only(Filter!(isFloatingPoint, args)).sum());
> }
>
> pure nothrow @safe unittest
> {
> 	assert(separateSum(2, 2.0) == tuple(2, 2.0));
> 	assert(separateSum(3, 2.0, 5, 1.0, 1.0) == tuple(8, 4.0));
> }

Thanks, that is exactly what I wanted to achieve. What is the 
performance implication of 'only' in this context? Will it copy 
all arguments?