I want to be able to filter a range based on a variable known at runtime. Something like this:

[code]
int id = getFilterID();

auto filteredRange = filter!(a => a.id == id)(rangeToBeFiltered);

[/code]

This doesn't seem to be possible, however as .filter only takes unary predicates. I tried:

[code]

filterString = "a.id == " ~ to!string(id);
filter!filterString(rangeToBeFiltered);

[/code]

But that also doesn't work. Is there another range algorithm that should be used in this case? Do I roll my own?

On Saturday, 20 January 2018 at 19:04:06 UTC, jsako wrote:
> I want to be able to filter a range based on a variable known at runtime. Something like this:
>
> [code]
> int id = getFilterID();
>
> auto filteredRange = filter!(a => a.id == id)(rangeToBeFiltered);
>
> [/code]
>
> This doesn't seem to be possible, however as .filter only takes unary predicates. I tried:

That should actually work. What exactly happened when you ran that literal code above?

On Saturday, 20 January 2018 at 19:09:28 UTC, Adam D. Ruppe wrote:
> On Saturday, 20 January 2018 at 19:04:06 UTC, jsako wrote:
>> I want to be able to filter a range based on a variable known at runtime. Something like this:
>>
>> [code]
>> int id = getFilterID();
>>
>> auto filteredRange = filter!(a => a.id == id)(rangeToBeFiltered);
>>
>> [/code]
>>
>> This doesn't seem to be possible, however as .filter only takes unary predicates. I tried:
>
> That should actually work. What exactly happened when you ran that literal code above?

... Huh. The code I posted was a simplified case of what I actually have and like a fool I didn't test it first. You're absolutely right, the above code does work. Color me embarrassed.

In the actual code, I kept getting DMD saying "...does not match template declaration filter(alias predicate) if (is(typeof(unaryFun!predicate)))".

I think it may be a scoping issue? I'll have to look closer at it.

Thanks for the help! Sorry I wasted your time. At least this pointed me in the right direction to find out what is really going on.