print int(0.5 + 0.695*100)/100;

[download]
prints 0.7 for me. Thereby showing that your round does not get the formatting correct which sprintf does, and still suffers from inconsistent rounding behaviour.

The reasons for this behaviour are basic to the fact of how floating point numbers work. They may not be readily predictable (exact details depend on your chip, OS, compiler, etc) but the underlying issue is that the internal representation of a floating point number is in base 2, while the visible one is in base 10. Therefore when you go to represent a floating point number, a nice round number base 10 turns into a repeating representation that is always stored with round-off error. What way you round in the boundary case depends on the interaction of that error and your operations.

In reply to Re (tilly) 1: strange rounding behaviour by tilly
in thread strange rounding behaviour by Anonymous Monk

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