buffered input (examples?)

[spir]

On 02/07/2011 03:40 PM, Michel Fortin wrote:
> On 2011-02-07 08:24:32 -0500, spir <denis.spir at gmail.com> said:
>
>> Does this have anything to do with currently discussed buffered input ranges?
>> If yes, how does such a design, or any alternative, fit their proposed
>> interface?
>
> You can build all of this on top of a buffered input range. The buffered input
> range is not an alternative for your complex parsing algorithm, it's just the
> component managing the buffer.
>
> Having the underlying range manage the buffer (as opposed to having your parser
> algorithm doing it) means that the buffer implementation can vary depending on
> the type of range. For instance, if you're parsing directly data in memory, the
> buffered range can use directly this data in memory as the buffer, requiring no
> allocation and no copy; if you're parsing from a file or a network stream it'll
> use a more standard buffer.
>
> But how exactly the buffer is implemented does not affect your parsing
> algorithm in any way. That's the great thing about it, separation of concerns:
> your algorithm will work independently of the buffer implementation used. All
> your parser algorithm has to do is say "shiftFront" and "appendToFront" to
> control what's available in the buffer.

Right, that's nice. But I was certainly unclear. My question was in fact how to 
make the lexeme stream be a buffered range. So that, precisely, the parser does 
not have to cope about buffering (or rather has to cope about it the std way 
clients will use to cope with buffered ranges once they are standardised).
In my hypothetical design, store() and unstore() are commands used to manage 
buffering, thus similar in purpose, but different from what Andrei's proposal 
provifdes. They just match the way I see a parser's needs, naively. Now, how to 
translate this design to make the lexeme stream a buffered range is very 
unclear for me; needed operations do not directly translate to appendToFront / 
shiftFront (unless I do not understand their action). I'm not even sure whether 
it would be simply correct to use a buffered range.

Denis
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