Re: How do I simulate variadic parameters for template (range) functions?

[Timon Gehr]

On 08/24/2011 07:40 PM, Andrej Mitrovic wrote:
Here's what I can do with a variadic function:
void main()
{
     int[] a = [ 1, 2, 4, 7, 7, 2, 4, 7, 3, 5];

     process(a[a.countUntil(7) .. $]);
     process(1);
}

void process(int[] vals...)
{
     foreach (val; vals)
     {
     }
}

Very simple, pass one or multiple arguments. But then I thought about
using the `until` template instead of countUntil. However `until`
returns a range. So my next guess was to write:

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

     process(a.until(7));  // ok
     process(4);  // error since 4 is not a range
}

void process(Range)(Range vals) if (isInputRange!Range&&
is(ElementType!Range == int))
{
     foreach (val; vals)
     {
     }
}

Is it somehow possible to automatically convert a literal to a range?
I really miss the convenience of variadic functions. I thought about
making an overload that only takes an int and constructing a simple
input range around it so it can be passed to process(), e.g.:

void process(Range)(Range vals) if (isInputRange!Range&&
is(ElementType!Range == int))
{
     foreach (val; vals)
     {
     }
}

void process(int arg)
{
     process(makeInputRange(arg));  // make an input range, pass to
above process()
}

But I can't overload templated and non-templated functions, I think
this is one of those old-standing bugs.

Workaround: You can make it a templated function with no template 
arguments and wrap a non-templated version, if it is important that the 
implementation is not a template.