something like filter[1] but that stops at first match? are there any native functions for this in D or I have to write one? just making sure to not reinvent the wheel


[1]: https://devdocs.io/d/std_algorithm_iteration#filter

On Fri, Mar 05, 2021 at 02:13:39AM +0000, Jack via Digitalmars-d-learn wrote:
> something like filter[1] but that stops at first match? are there any native functions for this in D or I have to write one? just making sure to not reinvent the wheel
[...]

Why not just .front?  E.g.:

	int[] data = [ 1,2,3,4,5 ];
	auto r = data.filter!(v => v % 2 == 0);
	assert(r.front == 2);


T

-- 
There is no gravity. The earth sucks.

On Friday, 5 March 2021 at 02:13:39 UTC, Jack wrote:
> something like filter[1] but that stops at first match? are there any native functions for this in D or I have to write one? just making sure to not reinvent the wheel
>
>
> [1]: https://devdocs.io/d/std_algorithm_iteration#filter

std.algorithm.searching.until

-Steve

On Friday, 5 March 2021 at 02:43:36 UTC, H. S. Teoh wrote:
> On Fri, Mar 05, 2021 at 02:13:39AM +0000, Jack via Digitalmars-d-learn wrote:
>> something like filter[1] but that stops at first match? are there any native functions for this in D or I have to write one? just making sure to not reinvent the wheel
> [...]
>
> Why not just .front?  E.g.:
>
> 	int[] data = [ 1,2,3,4,5 ];
> 	auto r = data.filter!(v => v % 2 == 0);
> 	assert(r.front == 2);
>
>
> T

it loops over the entire array then returns, I'd like to stop as soon as the predicate return true

On Friday, 5 March 2021 at 04:22:23 UTC, Steven Schveighoffer wrote:
> On Friday, 5 March 2021 at 02:13:39 UTC, Jack wrote:
>> something like filter[1] but that stops at first match? are there any native functions for this in D or I have to write one? just making sure to not reinvent the wheel
>>
>>
>> [1]: https://devdocs.io/d/std_algorithm_iteration#filter
>
> std.algorithm.searching.until
>
> -Steve

thanks, totally overlooked this searching section

On Friday, 5 March 2021 at 05:32:27 UTC, Jack wrote:
> On Friday, 5 March 2021 at 02:43:36 UTC, H. S. Teoh wrote:
>> On Fri, Mar 05, 2021 at 02:13:39AM +0000, Jack via Digitalmars-d-learn wrote:
>>> something like filter[1] but that stops at first match? are there any native functions for this in D or I have to write one? just making sure to not reinvent the wheel
>> [...]
>>
>> Why not just .front?  E.g.:
>>
>> 	int[] data = [ 1,2,3,4,5 ];
>> 	auto r = data.filter!(v => v % 2 == 0);
>> 	assert(r.front == 2);
>>
>>
>> T
>
> it loops over the entire array then returns, I'd like to stop as soon as the predicate return true

  void main() {
      import std.stdio, std.algorithm, std.range;
      int[] data = iota(5).map!"a+1".array;
      auto r = data.filter!(function (v) { writeln(v); return v % 2 == 0; });
      assert(r.front == 2);
  }

output:

  1
  2

'r' is an iterator. To force it to loop over the entire array that
would need a .array like I'm using for 'data'.

On Friday, 5 March 2021 at 02:13:39 UTC, Jack wrote:
> something like filter[1] but that stops at first match? are there any native functions for this in D or I have to write one? just making sure to not reinvent the wheel
>
>
> [1]: https://devdocs.io/d/std_algorithm_iteration#filter

std.algorithm.searching.find

To summarize.

* filter.front
* find.front
* until
* find

The first two provide you data at the first match, `until` produces a range exclusive of the first match.

If you just use find it will produce a range that starts at the first match, unlike filter the range includes everything and not just the matching data.