[mercury-users] Queries Clarifications for io.m

[Ralph Becket]

Noel  Pinto, Tuesday, 26 November 2002:
> 
> 1)io__flush_ouput flushes the output to the output buffer. What I 
> understand that it passes the result to the output buffer. ( What 
> do you mean flushing output to the output buffer)

Most IO operations are buffered by the operating system for efficiency:
it is cheaper to read and write many bytes at a time than individual
bytes.  Hence you cannot usually assume that a particular call to
io__write, say, will make any visible difference until you call
io__flush_output, which causes all buffered output to actually be
written.  Buffered output is often flushed automatically when you output
a newline (`\n').

> 2) io__output_stream retrieves the current output stream and does 
> not modify the IO state. What does it mean by that it does not 
> modify the IO state? Plz do explain.

What it says: calling this predicate does not modify the IO state in
any detectable way.  It merely tells you what the current output stream
is.

- Ralph
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