April 27, 2012
I'd like to know if there's a generic function over arrays to find the index of a specific elemnt therein, something like, say:

int indexOf(S) (in S[] arr, S elem);

which works the same way the std.string.indexOf() function works... couldn't find anything in the std.array module for this scenario. Would be nice to have this functionality built-in somehow.

Or is there a completely different / better approach to this in D?
Thx, M.

April 27, 2012
On Friday, 27 April 2012 at 19:49:33 UTC, M.Gore wrote:
> I'd like to know if there's a generic function over arrays to find the index of a specific elemnt therein, something like, say:
>
> int indexOf(S) (in S[] arr, S elem);
>
> which works the same way the std.string.indexOf() function works... couldn't find anything in the std.array module for this scenario. Would be nice to have this functionality built-in somehow.
>
> Or is there a completely different / better approach to this in D?
> Thx, M.

countUntil in std.algorithm should work fine.

http://dlang.org/phobos/std_algorithm.html#countUntil

Regards,
Brad Anderson
April 27, 2012
> countUntil in std.algorithm should work fine.
>
> http://dlang.org/phobos/std_algorithm.html#countUntil

Yup, it does! Just didn't see it there in the algorithm collection.
Thanks a lot.
April 28, 2012
On 4/28/12 3:51 AM, Brad Anderson wrote:
> On Friday, 27 April 2012 at 19:49:33 UTC, M.Gore wrote:
>> I'd like to know if there's a generic function over arrays to find the
>> index of a specific elemnt therein, something like, say:
>>
>> int indexOf(S) (in S[] arr, S elem);
>>
>> which works the same way the std.string.indexOf() function works...
>> couldn't find anything in the std.array module for this scenario.
>> Would be nice to have this functionality built-in somehow.
>>
>> Or is there a completely different / better approach to this in D?
>> Thx, M.
>
> countUntil in std.algorithm should work fine.
>
> http://dlang.org/phobos/std_algorithm.html#countUntil
>
> Regards,
> Brad Anderson

---
sizediff_t indexOf(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle);

Scheduled for deprecation. Please use std.algorithm.countUntil instead.

Same as countUntil. This symbol has been scheduled for deprecation because it is easily confused with the homonym function in std.string.
---

But isn't it the same funcionality? Why use a different name for the same funcionality?
April 28, 2012
On Saturday, April 28, 2012 12:18:57 Ary Manzana wrote:
> But isn't it the same funcionality? Why use a different name for the same funcionality?

It's _not_ the same functionality, even if it's similar.

std.string.indexOf varies drastically from std.algorithm.countUntil and in a way that easily leads to confusion if they're both named indexOf.

std.array.indexOf returns the index of the string that you passed in. That number doesn't say _anything_ about how many characters are before that sub- string. If str.indexOf("hello") returns 6, that's index 6, but it could be the third character rather than the sixth, because strings are UTF-8 and therefore variably-lengthed encoded.

std.algorithm.countUntil returns the number of elements in the range up to the range passed in and does not necessarily have any relation with any index (particularly if the range isn't random access). In the case of str.countUntil("hello"), it will return one minus the number of the character that "hello" starts at. So, if it's the third character, then the result will be 2, whereas the result of std.string.indexOf could have been 6.

Also, the result of indexOf isn't necessarily an index (particularly in the case of strings - but also in the case where a range is not random access), so calling countUntil indexOf is arguably a poor choice.

- Jonathan M Davis
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