protocol for using InputRanges

[Steven Schveighoffer]

On Thu, 27 Mar 2014 17:24:11 -0400, Walter Bright  
<newshound2 at digitalmars.com> wrote:

> On 3/27/2014 2:13 PM, Steven Schveighoffer wrote:
>> Note that a stream makes a terrible range, simply because of what you  
>> say --
>> reading is destructive, and determining emptiness is dependent on  
>> reading. You
>> need a buffered stream to make a good range, and then the logic becomes  
>> much
>> more straightforward.
>
> The range becomes the one element buffer in this case. It is completely  
> workable.
>

A 1 byte buffered stream? If it's performance you are looking for, you  
will not find it there.

> The range protocol is designed to work with streams. It's a giant fail  
> if they do not, or if you want to create a separate, non-range universe  
> to deal with streams.

Ranges work well on top of buffered streams, but not AS streams.

>> Even a single byte buffer is not enough, you need a bool to indicate  
>> the stream
>> is done.
>
> Right. But empty for a stream still has to read. Just follow the  
> protocol, and the range will work, even with streams.
>

A stream requires one primitive -- read. In one function call, you get the  
data you want, you can tell if it's empty, and the stream object does not  
need to concern itself with projecting a cached element. Adding range  
primitives on top of a stream does not make sense.

-Steve