On Mon, 28 Nov 2011 14:54:07 +0200, Steven Schveighoffer
<schvei...@yahoo.com> wrote:
On Sat, 26 Nov 2011 16:39:38 -0500, Walter Bright
<newshou...@digitalmars.com> wrote:
On 11/26/2011 5:46 AM, Steven Schveighoffer wrote:
Ranges are not good for reading N bytes from a file
descriptor.
Why not? Isn't that exactly what a range is supposed to be good for?
A range has a specific interface:
T front()
void popFront()
bool empty()
An input stream has a specific interface:
size_t read(ubyte[] buffer)
or alternatively:
ubyte[] read(ubyte[] buffer)
How does one map that interface into an input range? What is T? I
remember proposals where there was some extra function setFrontBytes, or
an additional parameter to front, that allows you to set the number of
bytes to read. This seems like trying to fit a square peg in a round
hole.
Now, a range fits very well on top of an input stream with a given
context. That context defines *what* front() is going to return. For
example, the next line of text.
But you still need a well-designed buffered stream interface that a
range can use to do its work from. Streams are not going to be the main
interface for most users, but they will be the tools that range
developers use to create easily iterated streams. And when the user
wants to read data from a file that has no well-defined T that you can
define a range for, the stream should provide all the tools necessary to
read that data.
Now, an output stream *does* fit quite well as a range, since an output
range's single put method coincides with an ouptut stream's write method.
-Steve
I was absent from range discussions, probably it has been said, sorry.
A ### range means, a structure which implements:
T front()
void popFront()
bool empty()
This matches with:
T peek()
void seek(1)
bool eof()
T is ubyte.
I believe we are asking the wrong questions, first question should be why
someone would like this simple range interface (3 functions) for streams?
Any use? Yes with these 3 we can do quite many things, not optimal but we
can. For the real use we need a new range.
T[] get(size_t)
bool put(size_t, T[])
bool seek(size_t)
...
Don't we need a range like this in any case? I doubt we can do much
without it.
