Challenge: write a really really small front() for UTF8

[Andrei Alexandrescu]

On 3/24/14, 1:06 AM, dnspies wrote:
> On Sunday, 23 March 2014 at 21:23:18 UTC, Andrei Alexandrescu wrote:
>> Here's a baseline: http://goo.gl/91vIGc. Destroy!
>>
>> Andrei
>
> Here's mine (the loop gets unrolled):
>
> dchar front(const char[] s) {
>    assert(s.length > 0);
>    byte c = s[0];
>    dchar res = cast(ubyte)c;
>    if(c >= 0) {
>      return res;
>    }
>    c <<= 1;
>    assert(c < 0);
>    for(int i = 1; i < 4; i++) {
>      assert(i < s.length);
>      ubyte d = s[i];
>      assert((d >> 6) == 0b10);
>      res = (res << 8) | d;
>      c <<= 1;
>      if(c >= 0)
>        return res;
>    }
>    assert(false);
> }

http://goo.gl/HBSv5T - looks nice! For minimum size replace the 
assert(false) with one inside the loop: http://goo.gl/eWs0ft

Andrei