counting words

[Benjamin Thaut]

Am 28.06.2013 18:42, schrieb Brad Anderson:
> On Friday, 28 June 2013 at 16:25:25 UTC, Brad Anderson wrote:
>> On Friday, 28 June 2013 at 16:04:35 UTC, Benjamin Thaut wrote:
>>> I'm currently making a few tests with std.algorithm, std.range, etc
>>>
>>> I have a arry of words. Is it possible to count how often each word
>>> is contained in the array and then sort the array by the count of the
>>> individual words by chaining ranges? (e.g. without using a foreach
>>> loop + hashmap)?
>>
>> If you don't mind sorting twice:
>>
>> words.sort()
>>      .group()
>>      .array()
>>      .sort!((a, b)=> a[1] > b[1])
>>      .map!(a => a[0])
>>      .copy(words);
>>
>> You could also do it with a hashmap to keep the count.
>
> Like so:
>
>      size_t[string] dic;
>      words.map!((w) { ++dic[w.idup]; return w; })
>           .array // eager (so dic is filled first), sortable
>           .sort!((a, b) { bool less = dic[a] > dic[b]; return less ||
> less && a < b; })
>           .uniq
>           .copy(words);
>
> It's a bit ugly and abuses side effects with the hash map.  The order
> will differ from the other program when words have identical counts.

I figured something like this by now too. Thank you.
But I don't quite understand what the copy is for at the end?

-- 
Kind Regards
Benjamin Thaut