Why does Perl's sprintf not round floating point numbers correctly?

Question

I was out looking for the rounding convention used by Perl\'s built-in function sprintf.

I was thinking that it does a normal rounding (e.g. ROUND_HALF_UP as in Java

Answer 1

This is a function of IEEE floating point numbers.

For more information, in a Perl context, see Perlfaq4 "Does Perl have a round() function" and in particular what it says about half-way-point alternation.