On Thu, 27 Mar 2014 16:58:12 -0400, Walter Bright
<[email protected]> wrote:
On 3/27/2014 12:50 PM, Andrei Alexandrescu wrote:
Yah, agreed. -- Andrei
Completely unworkable. To determine if a range is empty or not, it may
have to actually read from its input. TTYs are an example. Although
empty may then cache the result, and not read the second time it is
called, an observer of TTY could see that an item was read from the TTY.
In the land of ranges, it's construction and popFront that generally
advances the range. Empty does not. This is why assert(!empty) is all over
the place, it's considered to be non-destructive.
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 awkwardness for shoehorning streams into ranges I see is that the
advancement (popFront) and the check for termination (empty) are
decoupled, when in reality they are synced for a stream. This REQUIRES a
sticky bit for popFront to communicate with empty on whether it is EOF or
not.
Even a single byte buffer is not enough, you need a bool to indicate the
stream is done.
-Steve
