• jsako (14/14) Jan 20 2018 I want to be able to filter a range based on a variable known at
• Adam D. Ruppe (3/12) Jan 20 2018 That should actually work. What exactly happened when you ran
• jsako (11/27) Jan 20 2018 ... Huh. The code I posted was a simplified case of what I

jsako <spam spam.com> writes:

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?

Adam D. Ruppe <destructionator gmail.com> writes:

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?

jsako <spam spam.com> writes:

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.