http://www.perlmonks.org?node_id=109602


in reply to Re: Re: Using (s)printf()
in thread Using (s)printf()

Actually, this isn't quite the whole story. Most everyone follows the IEEE convention of "round towards nearest or even."
Examples (rounding all of these to the one's place):

2.51 becomes 3 (this is the 'nearest' rule, which always comes first)
2.49 becomes 2 (again, 'nearest')

However, what happens if you have 2.50 ? Which way do you round it... 'tis no nearer to 2 than to 3. The IEEE standard says if there is a tie, round to the even number.

2.50 becomes 2
3.50 becomes 4

You have to pick up or down... this method is consistent and thus tends to make your errors (statistically) smaller.

Replies are listed 'Best First'.
Re4: Using (s)printf()
by Hofmator (Curate) on Sep 03, 2001 at 15:32 UTC

    Actually, this isn't quite the whole story. Most everyone follows the IEEE convention of "round towards nearest or even."
    I'm aware of that - but it wasn't applicable in this case. Btw, (s)printf doesn't seem to get it right: 
    printf "%.15f", 0.5;  # prints 0.500000000000000
printf "%.0f",  0.5;  # prints 1 and should print 0

    [download]
    and 0.5 can be represented exactly ...

    -- Hofmator

[reply]
[d/l]

In Section Tutorials