On 9 Feb 2008, at 2:29 pm, Philip Weaver wrote:
GHC certain *could* do this, but it's arguably not the right thing
to do.
I have reminded the GHC maintainers before that the Haskell
specification
*REQUIRES* a Haskell system to support this; there is an example that
makes
no sense whatever without it. (And the other Haskell systems I use
get it
right.)
I note that David Bacon's SETL implementation has explicit support for
tying an input stream and an output stream together so that any time
input
is done on the input stream the output stream is flushed; this is done
automatically for sockets and is *seriously* useful in avoiding
mistakes.
Note that this should make essentially no difference to performance
because
(a) the flushing is only needed when the input buffer is exhausted,
which
happens once per line,
(b) the kinds of streams where you want it (terminals, STREAMs, sockets,
serial ports, &c) generally have other costs so high you won't be
able to measure this one,
(c) it *only* applies to bidirectional streams or to explicitly coupled
streams, so I/O to disc files or memory sticks or other high speed
block devices should never be affected at all (unless someone
chooses
to do it explicitly, in which case it's still going to be faster
than
anything they could have done by hand).
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