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

[monarch_dodra]

On Monday, 24 March 2014 at 16:31:42 UTC, Andrei Alexandrescu 
wrote:
> On 3/24/14, 2:02 AM, monarch_dodra wrote:
>> On Sunday, 23 March 2014 at 21:23:18 UTC, Andrei Alexandrescu 
>> wrote:
>>> Here's a baseline: http://goo.gl/91vIGc. Destroy!
>>>
>>> Andrei
>>
>> Before we roll this out, could we discuss a strategy/guideline 
>> in
>> regards to detecting and handling invalid UTF sequences?
>
> I think std.array.front should return the invalid dchar on 
> error, and popFront should attempt to resync on error.
>
> Andrei

That sounds good to me (I think). Better than a straight up 
assert anyways...

...which is what the code you submitted does.

Also, I think relying on bounds checking is wrong: Disabling 
bounds checking mean you are OK for memory corruption for *wrong 
code*. I don't think invalid string is wrong code. 'front' should 
do an actual "if", and "assert(0)" when needed. This should have 
no impact on performance BTW, if done with pointer extraction 
("slice.ptr[1]"), and in a trusted context.

Of course, this is all assuming we are asserting at all.