Because you are accumulating different rounding errors and (most likely) a shifting mantissa changes the last bit to be rounded.

update

Rounding is often not very intuitive, try to avoid if possible.

If you want to track the details you need to look into the binary representation and the underlying C lib.

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery FootballPerl is like chess, only without the dice


In reply to Re^3: $var == 1 fails when $var = 1 by LanX
in thread $var == 1 fails when $var = 1 by mjlush

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