LOOP + HANDLE

[Wolfgang Jeltsch]

On Wednesday, 2003-06-11, 18:54, Filip wrote:
> So how to write function that will wait until Handle is ready for reading ??

It would be very bad to use a while loop for this like
    while (!is_ready(handle)) /* do nothing */;
which is called active waiting. Your processor is busy all the time doing 
checks. Normally the operating system supports passive waiting which means 
that your thread is suspended until the respective condition is true and 
woken up then. I don't know to what extend the different Haskell libraries 
support this kind of waiting for your problem.

> And is there something like "if" ??

There is
    if <condition> then <value-for-fulfilled> else <value-for-not-fulfilled>
and the when function for I/O actions.

Wolfgang