On Thu, 31 Jul 2003 16:30:17 +0200, Andreas Pflug <[EMAIL PROTECTED]> wrote: >Well, to me it's not well-known that floating-point addition is not >associative
This is a case of theory vs. practice mismatch: In theory addition is associative, in practice there is only limited storage available for a floating-point number. Let's do an example with 3 significant decimal digits: a = 1000 internal representation: 1.00e3 b = 1 internal representation: 1.00e0 a + b = 1.001e3 which cannot be represented in our system, so it is rounded to 1.00e3 and we get a + b = 1000 a + b + b + b + b + b + b + b + b + b + b = 1000 when evaluated left to right, but a + (b + b + b + b + b + b + b + b + b + b) = 1.00e3 + 1.00e1 = 1.01e3 = 1001 Servus Manfred ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org