Proposal for SentinelInputRange

[Steven Schveighoffer]

On Thu, 28 Feb 2013 11:43:06 -0500, Walter Bright  
<newshound2 at digitalmars.com> wrote:

> On 2/28/2013 6:59 AM, Andrei Alexandrescu wrote:
>> On 2/28/13 2:37 AM, deadalnix wrote:
>>> I don't see how defining a specific sentinel range here helps.
>>
>> On first blush I agree. It may as well be a range that by convention is
>> sentinel-terminated, and there's calls to front and popFront but never  
>> to empty.
>
>
> Consider the following code from lexer.c:
>
>     p++;
>     switch (*p)
>
> Written using an InputRange:
>
>     popFront();
>     switch (front)
>
> That code is INVALID. This is why a SentinelInputRange is necessary. You  
> can't just use an InputRange in an invalid manner by convention.

Does switch(*p) include a case for 0?  If so, wouldn't it be equivalent to  
say if(empty) /* do stuff that case 0 does */ else switch(front)

-Steve