front stability

[Steven Schveighoffer via Digitalmars-d]

On 6/30/16 7:50 PM, Walter Bright wrote:
> On 6/2/2016 5:51 AM, Steven Schveighoffer wrote:
>> I have always treated ranges with this expectation:
>>
>> 1. front gets you the current element of the range. Calling front
>> multiple times
>> without calling popFront should get you the same value.
>> 2. popFront moves you to the next element of the range if it exists.
>
> Right. Also:
>
> 3. empty can be called multiple times in a row, and must always return
> the same result.
> 4. it is not legal to call front() on an empty range, but it is not
> required to call empty() first
> 5. it is not legal to call popFront() on an empty range, but it is not
> required to call empty() or front() first.

Jack, can you update the rules to reflect this?

>> I'd say violating the expectations of what popFront and front do is more
>> egregious than a particular use case, no matter how valid that case
>> is. I'd like
>> to fix this bug, but I see there were quite a few major D contributors
>> in the
>> camp that wanted this function to behave the way it is. So I'd rather
>> first
>> debate the merits here.
>
> This was debated at length in the past. The result was the rules above.
> Ranges that do not follow those rules need to be fixed. I don't think
> there's a need to debate it again.

Thank you, I will set up a PR to fix generate.

-Steve