16 Sep
2002
16 Sep
'02
11:41 p.m.
"Glynn Clements"
David Sabel wrote:
...
Look at this small programm:
module Main(main) where
main = echoTwice
echo = getChar >>= putChar
echoTwice = echo >> echo
while executing: the program reads first two chararcters and then it
writes
the characters, but in my opinion it would be right to read one character, then write one characater, then read, then write. What's the reason for it?
Buffering.
A deficiency of the current implementation of the IO system, I'd say. Reading from stdin ought to force a stdout (and stderr) buffer flush. The GHC IO libs used to do this. This is constant source of confusion for users & turning off buffering alltogether is a poor substitute for having the IO system do the Right Thing under the hood. --sigbjorn